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The Fast Diet by Michael Mosley and Mimi Spencer (2013): What to eat and foods to avoid


The Fast Diet - intermittent fasting book by Dr Michael Mosley and Mimi SpencerThe FastDiet Cookbook by Mimi SpencerThe Fast Diet (2013) is an intermittent fast, with 5 days a week of regular eating and 2 non-consecutive days a week of very low calories – also known as a 5:2 or “five-to-two” diet.

  • 5 days a week – eat anything.
  • 2 days – eat a quarter of your usual calorie intake – 500 calories a day for women, 600 calories a day for men.
  • When fasting, eat low-glycemic foods – mostly protein and vegetables.

Below is an outline of the food recommendations in the book.  Summary  |  Fasting days  |  Non-fasting days  |  Maintenance mode.  There’s a lot more in the book.

Get a copy of The Fast Diet – Amazon UK or Amazon USA – for the full benefits of the plan, recipes, and meal plans.
Also see The Fast Diet Recipe Book (Amazon UK) and The FastDiet Cookbook (Amazon USA) – for recipes with calorie counts and meal plans.

The reasoning behind The Fast Diet

This book claims that we are genetically built to occasionally gorge and then to have to go for long periods of time without having anything to eat. Fasting leads to longevity, reducing the amount of IGF-1 your body produces to minimize accelerated aging and cancer. Fasting also appears to switch on a number of repair genes in your body.

FastDiet foods – what to eat on fast days and non-fast days

  • Fasting days – 2 non-consecutive days a week, follow the restrictions below
  • Non-fasting days – The other 5 days, there are no limitations on what you can eat
  • Maintenance mode – How to eat when you’ve reached your goal weight

Do not follow this diet if you are pregnant or under 18 years old. The diet is not recommended for type 1 diabetics or people with eating disorders, or people who are already extremely lean.

If you have another medical condition, check with your physician before following this diet.

2 days a week – Fasting days

Choose two days a week, not consecutive. Mondays and Thursdays are a suggestion. You can add a third day if you want, however beware of “fast fatigue.”

Some people may experience headaches or constipation, particularly at first; these can generally be alleviated by drinking lots of calorie-free liquids and eating foods that are rich in fiber

Foods to eat in The Fast Diet fasting days

  • Types of food
    • Animal protein (if you want) – beef (e.g. sirloin steak), pork (e.g. lean pork loin, fat-free ham, bacon), chicken breast, fish (e.g. tilapia, salmon, tuna, mackerel, shrimp), eggs (boiled or poached)
    • Vegetables – aim for a wide variety – different colors, textures, tastes, shapes. E.g. asparagus, avocado, broccoli, broccoli rabe, cabbage, carrots, cauliflower, cucumber, edamame, eggplant, fennel, green beans, unlimited leafy greens (spinach, kale, chard, mustard greens, salad leaves, watercress), leeks, mushrooms, bell peppers, scallions, snow peas, a handful of cherry tomatoes, zucchini. Eat a wide range of different-colored plants, No fixed guidelines about eating them raw or cooked – “have both, often”. Be cautious about starchy vegetables as they tend to have a higher GL and calorific value – proceed with caution and don’t add butter. Eat onions in moderation because of their GI value.
    • Fruit – citrus fruits (tangerine or grapefruit in particular), a watermelon slice, an apple (eat the skin, seeds, and core), a handful of berries such as blueberries or a couple of strawberries, a fig, a small banana, a small mango
    • Nuts – almonds, cashews, coconut flakes (unsweetened), pistachios. Eat in moderation as nut calories quickly add up
    • Seeds – sunflower
    • Soup – light broth or miso soup
    • Carbohydrates – whole-grain bread or tortillas, whole-grains (oats, bulgur, couscous, quinoa, brown rice/brown basmati), beans and lentils. As an alternative to pasta or wheat noodles, try shirataki noodles
    • Dairy – low-fat or fat-free milk, cheese, cottage cheese, cream cheese, or yogurt
    • Flavors – including chili flakes, cornichons, cumin, fresh herbs, garlic, ginger, jalapeños, lemon juice, mustard, olives, pepper, soy sauce, Thai fish sauce, vinegar, wasabi. The cookbook refers to these non-carb flavor enhancers as the “fantastic five”: lime juice, soy sauce, fresh ginger, garlic, and Asian fish sauce
    • Use agave as a sweetener if required, as it’s low-GI. Or try a sprinkling of coconut
  • Other guidelines
    • Fast days should be low-fat rather than no-fat – a little olive oil, nuts, and (trimmed) fattier meats are included
    • Ensure that you get some fiber on your fast days – eat the skin of apples and pears, have oats for breakfast, eat plenty of green leafy vegetables
    • Your aim is to have food that makes you feel satisfied but stays firmly within the 500/600 calorie allowance – and the best options to achieve that are high in protein and foods with a low glycemic index
    • Weigh foods after preparing them, to get an accurate calorie count
    • Broadly speaking, a glycemic index GI over 50 or a glycemic load GL over 20 is not good, and the lower both figures are, the better.
    • Stay hydrated – find no-calorie drinks you like, and drink them in quantity. Water (hot or cold, perhaps with lemon, mint leaves, cloves, ginger, or lemongrass), coffee or tea (black and sugarless), miso soup, instant low-calorie hot chocolate
    • Choose your own preferred way to consume your 500 or 600 calories – could be one meal a day, breakfast and dinner, two meals with some snacks in between, or your own preference. On purely theoretical grounds, a longer period without food (e.g. breakfast and dinner with a 12-hour break in between) should produce better results than one when you eat smaller amounts more frequently. Aim for as long a fasting window between bouts of eating as possible, as this is where many of the benefits of intermittent fasting lie
    • As an alternative, try the two-to-two – fasting not from bedtime to bedtime, but from 2pm until 2pm – after lunch on day one, eat sparingly until a late lunch on the following day
    • Wait before you eat – try to resist for at least 10 minutes, 15 if you can, to see if the hunger subsides

Foods to avoid or limit with The Fast Diet fasting days

  • Stay within your calorie limit
  • Limit or avoid high-glycemic GI or GL foods. Watch out for high-glycemic potatoes and many fruits, as well as dried fruits such as raisins and dates, which can spike your blood sugar and are best left for the days when you are eating freely. Fruit juices also have a high sugar content
  • Avoid starchy white carbohydrates (bread, potatoes, pasta). It isn’t’t expressly discussed in the book, but implied that you should avoid sugar on these days; the cookbook says that as a rule you should avoid white carbs on a fast day
  • There are no guidelines on artificial additives and artificial sweeteners, but in general the book recommends “real” foods for the fast days so we assume these shouldn’t be included
  • Avoid full-fat dairy and butter
  • Remove the skin and fat from meats before cooking
  • Avoid alcohol – it merely provides empty calories
  • Avoid processed foods – they tend to have hidden sugars and not contain much nutritional value
  • Meal replacement shakes – the authors aren’t great fans and think real food is better, but if you find they help you can use them – choose a brand that is low in sugar

Having an extra cookie on a fast day would be antithetical to your goals – when you’re fasting, you need to think sensibly and coherently about your food choices and exercise willpower

Other 5 days a week – Non-fasting days

Foods to eat in The Fast Diet non-fasting days

  • Eat what you want – no foods are off limits

Note that after about 6 months of intermittent fasting, you may find that you eat half the meat you once did, unconsciously. You’re likely to consume more vegetables. Many intermittent fasters instinctively retreat from bread, while stodgy “comfort foods” seem less appealing and refined sugars aren’t as tempting as they once were

Foods to avoid or limit with The Fast Diet non-fasting days

  • No restrictions

Maintenance mode

Once you’ve reached your target weight or just a shade below, you can consider adopting the Maintenance Model to stay at your current weight and keep the anti-aging benefits of occasional fasting.

  • Fast on only 1 day a week or once every 8-10 days
  • Or consider adapting your consumption on non-fast days to eat more calorie-dense foods.

Health benefits claimed in The Fast Diet

The diet in this book claims to reduce the risks for: Alzheimer’s disease, asthma, cancer, dementia and cognitive decline, diabetes, heart disease, high blood glucose / high blood sugar, high insulin resistance, low mood, chronic inflammation, memory loss, overweight/obesity, skin complexion issues, stroke

It also claims anti-aging benefits

As always, this is not intended to be a replacement for professional medical diagnosis or treatment for a medical condition. Consult your doctor before starting a new diet. This page describes what the authors of the diet recommend – Chewfo is describing the diet only, and does not endorse it.

Get a copy of The Fast Diet – Amazon UK or Amazon USA – for the full benefits of the plan, recipes, and meal plans. Also see www.thefastdiet.co.uk for tips.
Also see The Fast Diet Recipe Book (Amazon UK) and The FastDiet Cookbook (Amazon USA) – for recipes with calorie counts and meal plans.

Buy now from Amazon
How has this diet helped you? Please add a comment or question below.


{ 145 comments… add one }

  • SandraM April 5, 2013, 1:06 am

    In the 2 fasting days, can we drink diet soda made by splenda? Thank in advance for your answer.

    • Penny Hammond April 5, 2013, 10:38 am

      They say there’s no clear answer on whether you should drink diet sodas or not, but you should exercise caution, have the diet soda if only that would get you through the day, and limit how much you drink – and drink water instead if you can. http://thefastdiet.co.uk/diet-soda-yes-or-no/

  • Jackie April 10, 2013, 10:32 am

    I have done 2 fast days so far last Friday and Monday – both went ok no major problems.
    But today(Weds) I am so incredibly hungry , having what I would usually have porridge and fruit for breakfast and a light sandwich lunch just hasn’t filled me. I have had to have some extra food because I couldn’t concentrate although I was busy at work. Is this a known symptom of starting this intermittent fasting and will it wear off?

    • Penny Hammond April 10, 2013, 11:36 am

      Just checking – you’re supposed to be fasting two days a week, and you fasted on Friday and Monday – I presume this isn’t a fast day?

      Guidance on feeling hungry on fast days – people say that it will pass. Drink water and distract yourself. See http://thefastdiet.co.uk/inspiration-from-eleanor-d/, and also http://thefastdiet.co.uk/wol/.

      If it’s not a fast day… I can’t find any references to this, as you can eat as much as you want on non-fast days. It could be something to do with hormones as it sounds like most of what you were eating was carbohydrates…

      • Suzanne October 31, 2013, 7:43 pm

        Try a celery stalk when you are starving. It takes a while to eat, has almost no calories, requires you pay attention to it as you eat and tastes good. Another thing I use is madrilene. A mixture of beef broth and tomato juice. Use a beef base that has 15 calories per teaspoonful and about 12 ounces of hot water 1/2 tspn of beef base ans 1/2 cup of tomato juice is a satisfying break drink for about 30 calories. I had those “hungry” days even before I began the 5/2 diet. Then I just ate. I also find low cal soups to be great dinners on fast days. 8 to 10 ounces of cabbage, 2 ounces of smoked sausage, 4 ounces of potato1 tspn chicken soup base and water to cover generously plus whatever seasonings you like (bay leaf, cumin seeds, garlic, freshly ground black pepper) add a small diced tomato if you wish. You will come out near 300 calories and can have several smaller servings at intervals. I do this all the time and have lost about a pound a week since I began. Now down about 18 pounds. I don’t use the same two diet days every week but vary them to suit my schedule.
        Just look up the calories in what you enjoy and create your own favorites!

  • John Fitzgerald April 11, 2013, 3:50 pm

    I have already started your fast diet.


    How can I flush the fats out of my blood????

    • Penny Hammond April 11, 2013, 7:25 pm

      As far as I can tell, the book doesn’t talk about flushing the fats out of your blood.

  • Karen Thompson April 23, 2013, 1:37 pm

    I am starting day one of fasting, I understand what I should not eat and that keeping within you caloric limit of 500 calories. AM i understanding correctly that I need to fast 2 non-consecutive days? Do I chose two days a week and stick to those? I saw a suggestion that said Tuesdays and Thursdays. Instead of every other 2 days….what is the best and most effective way?

    • Penny Hammond April 23, 2013, 5:56 pm

      Pick two days when you’re unlikely to want to eat or drink a lot – most people choose weekdays because they prefer to have fun with what they eat and drink at weekends. Many people avoid Fridays for that reason. The author suggests Mondays and Thursdays – think of what will work best for you.

  • Marylou April 24, 2013, 8:04 am

    What of exercise on fast days…? Normal..or conserve energy? Cheers Marylou

  • Darren April 25, 2013, 4:01 pm

    Hi,I have completed my two fast days,monday and Thursday,mainly by cuppa soup and fruit,I just wanted to clarify,on the eat anything days,what would be a recommended calorie intake to maintain weight loss but also keep up energy levels for an adult male with a physical job,thanks.

    • Penny Hammond April 25, 2013, 5:22 pm

      When they say eat anything, they mean eat anything – pizza, cookies, whatever you want to eat without calorie restrictions or other restrictions. That’s probably why the diet has become so popular!

  • Mick Cameron April 27, 2013, 4:47 am

    Hi Penny,
    I saw the show and am going to purchase the book.
    I am keen on doing the 3.5 days that Michael fasted for on the show and then jump into the 5/2 diet.
    Correct me if I’m wrong, but I think this would be a more beneficial start from a longevity point of view.
    Will you please tell me what type/brand of soup Michael had during his 3.5 day fast?
    Thanks so much.

    • Penny Hammond April 27, 2013, 1:05 pm

      Hi Mick, I haven’t been able to find the type/brand of soup, but it’ll be low calorie and probably low carb as well (as high-glycemic carbs can make you feel hungry) – vegetables, maybe meat/poultry/fish, and possibly beans or lentils. Some people use dried or canned soup, others make their own. By the way, if you’ve been eating a lot of processed foods and not many vegetables or much fiber, you may have trouble with a fast lasting several days, so eat lots of veggies before you try it. Hope that helps.

      • michelle May 13, 2014, 8:55 am

        Hi. I’m starting my 4 day fast. He used Miso Cuppa soups, I don’t think the brand is that important, they are salty and take the edge of the hunger. I’ve used them when I’ve done 2 day fasts. very little calories, the ones I got were 60 calories give or take.

  • Jackie M April 28, 2013, 1:09 am

    Hello Penny,
    Just finished reading the info/comments re this Diet/Eating Plan and found them very helpful. 7 days ago I started doing 3 x Fast and 4 x Eat days (I have a large amount of weight to loose). After 7 days I have only lost 500g, but am happy with this. I have been on practically every diet known to man over a period of many years and feel sure if I had never dieted I would not be as heavy as I am today. I vowed I would never diet again, but after seeing a TV item about the 5/2 idea and success, decided to give it a go. I am 67 years old so slow continual weekly weight loss is fine. I am eating 3 x small meals a day: Breakfast (100 calories) small egg & small fruit, Lunch (200 calories) large salad & small protein, Dinner (200 calories) vegetable stir-fry or soup & small protein. I use herbs, spices, vinegar, organic soy sauce, organic miso soup paste. unlimited, water, black tea and limited black coffee. I have kept strictly within the 500 calorie allowance. Unfortunately I have not been able to clarify the following:
    1) Do 3 x Fast Days work better/quicker than 2 x Fast Days (especially if you are very overweight) ?
    2) Are eating 2 x meals rather than 3 x meals on Fast Days more beneficial ?
    Any feedback you may be able to provide regarding these queries would be much appreciated. With thanks.

    • Penny Hammond April 28, 2013, 6:20 pm

      The authors suggest sticking with 2 days a week to avoid getting “fast fatigue” – if you get tired of fasting, it’s definitely not going to work! It’s probably best not to try to out-fast the fasters; stick with 2 days a week.

      They say that this method hasn’t been studied enough to know if it’s better to eat 2 meals a day rather than 2. Mimi (who’s already skinny) tends to graze through the day, and Michael has 2 meals a day – around 250 calories for breakfast and 350 calories for supper – effectively fasting for around 12 hours at a stretch. Some people find having 1 meal a day better. It’s possible that it’s more beneficial to leave longer periods between meals, as Michael does, but that’s a theory. Again, do what works for you and you can carry on doing long term.

  • Sue April 28, 2013, 4:28 am

    I have high blood pressure, have had two TIAs, a pulmonary embolism and am borderline diabetic 2. Can I still follow this diet?

    • Penny Hammond April 28, 2013, 4:36 pm

      You should check with your doctor if you have a medical condition.

  • Dee Para April 29, 2013, 9:26 am

    Hello Penny, My husband and I just started the FastDiet (5/2- feast/fast days)-we saw the PBS show & was very impressed & decided to buy the book & give the diet a try. We did it on a Saturday to monitor our progress. We stayed busy during the day & also did a 6 mile bike ride. My husband felt okay on the fast day, at 10:00 am we had oatmeal and blueberries (190 calories), added one slice of whole wheat toast (100 calories) for my husband. For dinner at 6:00 pm had the chicken stir-fry (306 calories) as listed on page 131 in the book. As I said earlier- my husband was okay, however, for me at 4:00 pm I had a very bad headache that would not go away. I did not prep the meal the day prior & this was a huge mistake- at 5:30 p.m, I started to prep the evening meal – I had low energy & my headache was getting worse. After having dinner, I still felt like I had very low energy, ended up going to bed early. The next day- I had an engish muffin & international hazelnut coffee- both items tasted so good. I have low blood sugar- will this detail effect me on my fast days? If so, then what do you suggest? Do I need to add more calories on my fast days? to help with having very low energy? Thanks for your advise,

    • Penny Hammond April 29, 2013, 11:52 am

      There could be lots of reasons for getting a headache – you could have been dehydrated; you could have withdrawal from something you usually eat/drink but didn’t do on that day; you could have hormonal headaches or allergies; any number of reasons! Oatmeal and blueberries is a relatively high-carb meal; your blood sugar could have dropped as a result and you didn’t have enough protein/fat/energy to carry you through the rest of the day until dinner. You could try a fast day again when you’re fully recovered and see what happens; it may have been unrelated to the fasting. If the same happens again, check with your doctor.

      • Dee Para April 29, 2013, 2:33 pm

        I will try the 2nd fast day with eating more protein for breakfast to see what happens. I did drink plenty of water on the 1st fast day. I will let you know how it turns out. Thank you! & have a great day!

  • Bill S April 29, 2013, 9:38 pm

    I’m in my second week of the 5:2. Reading the replies it sounds like most of the people are really intent on getting their 500 calories on fast days. I can’t do it that way. If I eat a little it just causes me to get extremely hungry. On my fast days I eat nothing and only drink black tea all day. For me, just biting the bullet and staying away from food makes it much easier.

    • Theresa May 11, 2013, 10:55 pm

      Thats what I think too. I’m going to start this Monday (just heard about yesterday-Friday) and I’m going to do it only with water tea. I don’t think black coffee is a good idea because it raises insulin and endogenous blood sugar and that will just make me hungrier. This was my only question and I’m so glad I saw your comment!

  • Elaine deBeaux May 5, 2013, 6:12 am

    I have blood sugar problems. Elevated. I’m trying to do the fast diet but get really fuzzy and dizzy on fast days. Chris Kessler says it’s not good for blood glucose to fast but I thought if I push thru I’ll be fine? I eat 100g ricotta half pear and few reaspberries. Sorry but I’m just over eggs. Then at night have the allowable meat vegs. Just need to know if others have same problem and if they have pushed thru it. I drink lots water and rosehip tea.

  • Diarmuid May 7, 2013, 9:55 am

    I’ve been on the 5-2 for 3 weeks & I’m finding it really easy and can already see the benefits. However today I accidentally ate about 150 cals over my 600 limit. Would this have a negative effect on my progress?

    • Penny Hammond May 7, 2013, 10:30 am

      Accidents happen – don’t worry about it!

  • Liz May 7, 2013, 5:51 pm

    Hi Penny,

    I’ve been doing the 5:2 diet since September, so more than eight months. I’ve stuck to it religiously, apart from over Christmas when I had a week’s break. Rather unbelievably I have put on weight. On fast days I usually only eat fruit and veg, so raw carrots, salad, tomatoes, apples and bananas primarily. I think my calorie intake is probably less than 500 but I do drink several cups of tea with skimmed milk each day. I’m puzzled and not a little frustrated by the results. Any advice?

    • Penny Hammond May 8, 2013, 12:57 pm

      Hi Liz,
      Try this – write down everything that you eat and drink on a fast day, and use a calorie calculator to check the number of calories (there are a lot of them online). The calories in the tomatoes, apples, and bananas might be adding up.
      Another suggestion – if you’re grazing on these foods throughout the day, try concentrating them in a couple of meals, say breakfast and dinner, so you have long breaks without eating.

    • Theresa May 11, 2013, 10:57 pm

      Or try having water and tea only? Also, are you exercising on non-fast days at all? Just some thoughts.

    • Hope July 10, 2014, 3:44 pm

      It could be too much skim milk that puts you over the edge and all the veggies and fruit add up if you eat enough

  • David W May 12, 2013, 9:34 am

    Hi all
    I have just read this fantastic book and am ready to start my first fast day tomorrow! However, when I came to pick one of the menus provided, I found some discrepancies between the calories in the menus and the ones in the tables in the back of the book? Has anyone else found this? Sometimes its not much and sometimes its way out (see the blueberries on page 141!)

    On checking other websites for the calories counts of certain foods, I found even more inconsistencies! Am I getting to hung up on this? What’s the best source of truth!!

    Thanks all


    • Penny Hammond May 12, 2013, 5:04 pm

      Natural foods can be inconsistent – if an animal eats differently from another one, or a plant has different growing conditions, that can affect the number of calories. Units of measurement are sometimes different in different countries, and that can confuse matters even more. And on top of that, there are disagreements about how things like calories should be measured – some of the most popular measurement methods don’t take into account things like the difference in calories between the same food if it’s raw or cooked (cooked foods often have higher calories as the structure breaks down and calories are made available).

      Don’t get too hung up on the exact numbers, if possible – they should be directionally correct.

  • Josie Kulp May 13, 2013, 1:11 pm

    Am I NOT to drink any coffee while fasting?
    Thank you

    • Penny Hammond May 13, 2013, 3:14 pm

      Hi Josie,
      The book says that black and sugarless coffee is okay while fasting.

      • Hope July 10, 2014, 3:45 pm

        I drink coffee with creamer and just include as my 500

  • eleanor bistrian May 14, 2013, 2:20 pm

    I was very happy to find a diet that was logical for both health and weight loss. I have now been on the diet for eight weeks with a weight loss of only two pounds this is very discouraging as you can imagine! I have followed it completely with no exceptions and I also work out at the gym three days a week. I have a normal BMI and really only wanted to lose 6 to 8 pounds. What I am trying to find out is how has this failed for me or do I need more patience with it? I would certainly appreciate any info you could give me. sincerely, Eleanor Bistrian

    • Penny Hammond May 14, 2013, 8:11 pm

      Hi Eleanor,
      There aren’t really any guidelines in the book for this situation. If you have a normal BMI, your body could be telling you you’re the right weight.
      A few things that you could try: varying the number of meals you have on your fast days(e.g. one meal instead of two); drinking more water on all days; eating more veggies and reducing processed / high glycemic foods on non-fast days.

  • Melinda May 15, 2013, 8:05 pm

    Can you abstain from eating and only drink water on the fast days? Making them zero calorie days.

    • Penny Hammond May 16, 2013, 12:40 pm

      That’s not what’s recommended in the book.
      There’s a lot of discussion here: http://thefastdiet.co.uk/different-ways-of-managing-your-fast-day/ (click on “click here to join us” to see discussion)
      My personal thought – if you eat a LOT of veggies and no processed food on your non-fast days, you may be able to get away with fasting completely, but if your eating habits are more standard you’re likely to get blocked up and cause yourself more problems. One of the advantages of this diet is that it encourages you to eat more veggies (and some fruit), providing fiber and nutrients.

  • A Reader May 21, 2013, 5:59 pm

    The 2 fast days are non-consecutive days? I thought it was 5 days of eating and then 2 days of fasting.

    • Penny Hammond May 21, 2013, 6:06 pm

      5:2 looks like it should be 5 days of eating then 2 days of fasting, doesn’t it? It’s a little misleading – they recommend that the 2 fast days are non-consecutive.

      • Jolebon June 13, 2013, 2:06 am

        What happens if the only days which I can fast on are consecutive? Will that be worse than say, just fasting once a week?

        • Penny Hammond June 13, 2013, 10:57 am

          It’ll be tough fasting for two consecutive days, but it’s an option.

  • Jeppe May 23, 2013, 11:10 am

    Does the fast days have to be the same each week? Or can i change, if i want to?

    • Penny Hammond May 23, 2013, 12:08 pm

      You can vary your fast days if you want, for example if it’s a holiday or if you have a social event with a big meal.

  • CC May 23, 2013, 3:40 pm

    I want to try this diet. I have been successful at Weight Watcher’s, but would like to have another option. What I am concerned about is the non-fast day. What is typical, I know it says it what ever you want, but what about portion control. What works best?

    • Penny Hammond May 24, 2013, 11:24 am

      They literally mean eat what you want, no portion control, on non-fast days. They say the benefit comes from the fasting periods themselves, where your body gets to rest and experience scarcity.

  • Tammy Bushell May 23, 2013, 7:15 pm

    Hi Penny,

    I’ve been doing the fast for 3 weeks now but I’m spreading each fast “day” over 2 days (i.e. eat lunch Tuesday, then stick to the 500 until having a late lunch on Wednesday), as this is psychologically easier for me. I haven’t seen any weight changes yet, although I know it may not happen immediately; will this 24hr system be as effective as a morning to night fast? Perhaps sleeping in the middle of a fast effects the outcome?

    • Penny Hammond May 24, 2013, 11:21 am

      Hi Tammy,
      Spreading the “fast” over two days as you describe is an option. You end up having a shorter fasting period – instead of two nights and one day of fasting, you only have one night and one day, so your body has approximately 8 hours shorter in fasting mode. If that works for you, great!

  • Jeppe May 24, 2013, 1:44 am

    Thx Penny :0)

  • CC May 24, 2013, 11:39 am

    Does the book address how to transition from another diet like Weight Watchers, my calorie restriction every is around 1200, so I am worried about gaining weight because I will take in higher calories on my non-fast days

    • Penny Hammond May 24, 2013, 11:54 am

      There’s no guidance on transitioning from other diets in the book – it just says eat whatever you want on non-fast days, no restrictions. If you’re not comfortable jumping straight to “eat everything on non-fast days,” perhaps you could try this in the interim: Continue to follow the WeightWatchers Good Health Guidelines that you’re used to on non-fast days (lots of veggies and fruits, whole grain where possible, milk, healthy oils, enough protein, limit added sugar and alcohol, drink 6-8 glasses of water a day) but take it easy on the calorie limit. That way you would get enough calories over the course of the week, without your body kicking in to “I’m starving, I need to store fat” mode.

  • CC May 24, 2013, 1:10 pm

    Thanks Penny, that is what I was thinking. Sounds like a good idea.

  • Denise May 29, 2013, 7:48 pm

    Hi, could someone tell me if I’m doing this wrong or right please. After having my tea at say 5pm on a Monday I don’t eat anything until 2pm (20 hours) on the Tuesday at which time I have a 230 cal shake, I then wait till around 5pm ish and have a meal of 270 making up my 500 calls. I then have nothing until the next morning (wed) to get up and have whatever I want for breakfast. So in effect I’m going 39 hours will 500 calls in between. A I doing this right.

    • Penny Hammond May 29, 2013, 7:51 pm

      That sounds like you’re doing it about right, according to what the book says. Just make sure you’re not restricting food on the day before or the day after the fast day.

  • kaz.bah@live.com May 31, 2013, 1:21 am

    I eat my evening meal around 730 on non fast night then dont eat again til 2/3 pm on fast day and use the rest of my calorie count for dinner,then not eating again til the next morning. I am finding it very easy to maintain, which is strange as I am usually hungry all the time even though I eat healthy meals. I try to stick to around 1200 calories every other day and will have a splurge once a week. I have restrictions with exercise as I have a spinal injury, but walk as much as I can each day….I am trying to be healthy but also lose weight gained from no longer being active through work,as I cannot work anymore….Am I on the right track..overall? cheers

    • Penny Hammond May 31, 2013, 11:05 am

      Your timing sounds about right.

      According to the book you’re not supposed to restrict calories on non-fast days. If you’re tiny and not very active and having splurge days, you probably don’t need as many calories as some other people, although 1200 calories sounds low. You can check your needs on a tool like http://caloriecount.about.com/tools/calories-burned

  • Maria May 31, 2013, 5:16 am

    Tell me if im doing this right please

    Monday Fast day starts at 8pm (after i finish my normal Dinner)
    Then I go to bed.
    Have nothing to eat uptill Tuesady 8pm ,
    Then have normal Dinner (Back on feed day)
    Question is can the 500 calories be added in the 24 hour period? between the Mon 8pm – 500 cal- Tues 8pm ?

  • Maria May 31, 2013, 5:20 am


    start clock 8pm
    500 calorie

    • Penny Hammond May 31, 2013, 11:09 am

      Hi Maria,

      What you’re describing is an alternate timing known as a “24 hour fast.” The authors say you’ll lose weight more slowly using this timing instead of the general recommendation they use, which is:

      Day with no restrictions, ending with dinner and late night snack
      Start clock when you finish eating for the day
      Wake up
      500 calories over the course of the day (or 600 calories for a man)
      Wake up
      Day with no restrictions

      However, if you find you can’t sleep because you’re going to bed hungry, the 24-hour fast might be better for you

  • Rhia May 31, 2013, 7:30 am

    Can you let me know is it a bad idea to restrict calories on a non fast day? For instance if I eat around 700 calories on a non fast day will it inhibit my weight loss or help it?

    • Penny Hammond May 31, 2013, 11:15 am

      Hi Rhia,
      700 calories is definitely not a non-fast day! To follow this diet, you shouldn’t be counting calories on non-fast days.
      If you’ve spent a long time restricting calories every day, you might find it beneficial to let yourself eat until you’re full on non-fast days – so your body doesn’t think that it’s starving.

  • kaz June 1, 2013, 12:16 am

    Thanks for the reply…..I have always averaged 57/59 kilos and been slim……its only since my injury that I have gained the weight, thats the reason i stay around the 1200 as I seem to put on weight too easily and due to not being able to be as physical as I used to be,I cant shake it either.This diet seems to be the best shot at losing some weight,but will see how things go.I have done 11 fast days and the scales say 2.5 down but of course measurement wise no change yet…I have gain 10kgs over the 3years since my injury, cheers

  • Maria June 3, 2013, 8:48 am

    Hi Penny

    what page in the book does it explain this. They even said to do 2pm to 2pm ? Isnt that the 24 hour cycle.
    the other way is like 36 hour fast ?

  • PWR June 4, 2013, 2:50 am

    Been on the 5:2 for 2 months and consistently lose about a pound a week, which is the avg weight loss for most people. Drink lots of water to avoid a headache and make micro adjustments once in a while to suit your schedule. Changing what I eat on feast days doesn’t seem to make any difference, so bring on the bacon, dark chocolate and butter – it all seems to work. I have had to buy new pants and look forward to my next lipid panel, when I can tell my Doctor to take his statins and BP meds and go to h&ll! I am 57, now at 195lb (down from 216) and this is the most game changing, sustainable and reasonable approach to not just weight, but to many other metabolic issues as well. It also REALLY helps to lean towards a more Paleo diet when beginning this lifestyle change. You won’t feel nearly as hungry if you cut your carb and sugar intake at the same time, and it will work faster and better. If you are middle aged and continually fighting with yourself about health and diet… This will make you feel very liberated.

  • Richard June 14, 2013, 7:14 am

    I’m male 48yo and (was) 15kg’s overweight. after 4 weeks on the 5:2 diet i’m now 10kg’s overweight. my belt has tightened 2 notches, I look and feel better, my wife compliments me. just a 30% loss from the total desired makes such a change to lifestyle and self-feeling. the diet is usually very easy, the benefits of health in longevity are obvious as you just feel the calories evaporating whilst just sitting there. thankyou Dr Mosley your show and book have changed my life. moving forward if I gain some weight I will know exactly how to drop it back down again.

  • George June 16, 2013, 6:37 pm

    Can exercise as in weight training to become bigger and stronger be done on a 5:2 diet. My understanding by being on the 5:2 diet you are reducing your IGF1 levels, for muscles to increase in size do you not need high levels of IGF1.

    Could I be on the 5:2 diet and have the benefits it promotes ( loss of fat etc) and increase size and strength through weight training for sport that I’m involved in.


  • CC June 24, 2013, 10:18 am

    I tried this for 1 week (switching from weight watchers). I followed 5:2 to a tee and gained 1 lb, very, very disappointed, I so wanted it work for me…

    • Penny Hammond June 24, 2013, 10:52 am

      Sorry to hear that.
      You could try it for a little longer to be certain what the effects of the diet are for you – a 1 lb fluctuation after a week could be from other factors.

  • Charity June 24, 2013, 3:23 pm

    Thank you for the wonderful help you’ve been giving, Penny.

    I’m on my 2nd fast day, and feel great. I just have 1 question – I just cannot seem to stay within 500 calories. I am logging each and everything using an online calculator, and unfortunately things like the teaspoon of honey and tablespoon of psyllium and chia make me go over the 500 calories by around 50-60 calories.

    I’m ending up closer to the 600 calories mark (I’m a woman, so am trying to follow the 500 calories suggestion in the 5:2 diet). Do you think this is a really serious transgression? I figure the other 5 days I eat around 1600-1800 calories, max 2000 on days I go out. So over the week, I’m still averaging below 1800 or so.

    FWIW, although I’m still starting out, I just wanted to say this is the first time in over 30 (of my 50) yrs that I have not obsessed about food on my non-fast days. In fact, I seemed to have lost that constant worry I have. So I actually ate better w/o even trying!

    It is this destructive obsessing that I am hoping to resolve by sticking to this 5:2 diet or really I should say eating plan as it’s a way I can maintain forever, I hope.

    • Penny Hammond June 24, 2013, 4:28 pm

      Thanks for your message – I’m really happy to hear that you’re not obsessing about food on your non-fast days! Without that constant stress, hopefully your body will recognize that you’re not likely to starve and will let you lose some weight as a result.
      I think it’s probably not the end of the world that you’re going 10% over – just keep an eye on it to make sure it doesn’t increase. And it’s possible that that teaspoon of honey makes you hungrier on those days – if you can wean yourself off it, that might make fast days easier.

  • Charity June 24, 2013, 9:15 pm

    Thank you so much for weighing in, Penny.

    I try to eat mostly protein and fiber w/ minimal starch/carbs, so honey is the only added sugar I’m using. I will try to stop it though on fast days.

    Today was a rough day but in my defense, it is only my 2nd fast day. ;P I exceeded the calorie limit, but onward and upward until the next fast day.

    Best wishes to all my fellow IF/5:2-ers!

  • Kate June 30, 2013, 5:11 am

    Hi there, I do a lot of exercise most days and weight train but looking to start the 5:2 for my summer holiday in a month. Can i comsume more than 500 calories if I am exercising on my fast days?



    • Penny Hammond July 1, 2013, 10:47 am

      Hi Kate,
      There’s a discussion on exercise on the Fast Diet at http://thefastdiet.co.uk/intermittent-fasting-and-exercise/ (click on “click here to join us” at the bottom of the page to see the discussion). Exercise isn’t seen as a reason to increase calorie consumption on fast days.

  • Jan July 10, 2013, 7:46 am

    I am just wondering if I need to eat as much as 500 cals if I do not feel hungry. I have porridge with fruit for breakfast, made with semi skimmed milk and several cups of tea during the day also with semmi skimmed milk. I have added up total calories to be around 350 and as I am really busy on the day I fast so don’t have time to feel hungery. Is this ok

    • Penny Hammond July 10, 2013, 3:32 pm

      There aren’t any hard and fast rules – it sounds like that pattern works for you.

  • Clare July 16, 2013, 2:30 pm

    Hi can I fast from 4pm one day until 6pm the next. I think I find this much easier?

    • Penny Hammond July 16, 2013, 2:35 pm

      Yes, you can – the authors call this a “24-hour fast” and say you’ll lose weight more slowly this way.

      • Clare July 16, 2013, 4:40 pm

        Thanks, will I still get the health benefits?

        • Penny Hammond July 16, 2013, 7:13 pm

          The authors say that research is still being done to find out how different lengths and degrees of fasting can benefit your health – but a shorter fast could still benefit you.

  • Jacqueline July 24, 2013, 3:50 am

    I am following a fairly strict calorie-controlled diet on my non-fast days. (1500 a day)
    Is this OK, and safe to do?
    Thanks, J.

    • Penny Hammond July 24, 2013, 9:00 am

      If you do that, your body’s probably in “help, starvation!” mode all the time – which won’t help you lose weight in the long run. On non-fast days, try eating at least the number of calories you need for your height and activity level.

  • Joan Blake August 2, 2013, 8:51 am

    Have started the 2-5 diet this week. Reading all the comments about the programme Michael Mosley did through Horizon. I am wondering if one can buy a DVD of the programme?

    Thanking you

    • Penny Hammond August 2, 2013, 3:03 pm

      I haven’t found anywhere to buy it, but you can see it online – search for Michael Mosley Horizon video – I can view it at http://vimeo.com/54089463.

  • Kimberly August 6, 2013, 11:02 pm

    Hi! I tend to go over my 500 calories on my fast days; a little bit of hazelnut creamer here, a few extra crackers there, etc…. nothing really outrageous, but when that happens would it benefit to do a fast day, the next day, since I went over on my 500 calories the previous day therefore rendering the fast day as a non fast day? Thank you for your time!

    • Penny Hammond August 7, 2013, 10:01 am

      Hi Kimberly,
      Try to stick to 2 days a week and 500 calories – if you don’t follow the diet on a fast day, don’t try to compensate the next day.

  • kriti sharma August 11, 2013, 12:48 pm

    is it ok for a person suffering from IBS to do this?

    • Penny Hammond August 11, 2013, 1:23 pm

      The authors say that the diet is not recommended for type 1 diabetics or people with eating disorders, or people who are already extremely lean.
      They don’t mention IBS, but do say that if you have another medical condition you should check with your physician before following this diet.

  • kriti sharma August 11, 2013, 1:42 pm

    thanks penny! yea i was gonna try it today I couldn’t i just ate my GF bread :/

  • kaz August 14, 2013, 2:25 am

    I have been following the 5;2 for a few months now and have been walking and doing hand weights. I usually am under the 500 cals on fast days and have gone up from 1200 cals daily to 1500/1900 on feed days…no weight lost yet….I know its for health but very disheartened when I read how the weight seems to just fall off others……I am desperate to lose a few kilos…….whats going wrong, I generally eat pretty healthy food with some indulgences..thanks

    • Penny Hammond August 14, 2013, 9:58 am

      There aren’t any guidelines in The Fast Diet book for what to do if you’re not losing weight, although there’s some discussion at http://thefastdiet.co.uk/forums/topic/not-losing-weight/ – click on “click here to join us” at the bottom of the page to view the discussion. .

      Have a look at The 5:2 Diet Book by Kate Harrison Step 1 – pages 96-110. What this book says is that to lose weight, you should have a calorie deficit each week, when you combine the calories from your fast days and non-fast days/feast days. That book gives you details on how to calculate your daily calorie requirement and use it to work out how much you should be eating on non-fast days/feast days. There’s a Chewfo food list for The 5:2 Diet, if you’re interested, but it’s related to what to eat and foods to avoid and doesn’t have the calculations.

  • Em August 18, 2013, 2:10 pm

    I’m curious – on a fast day, if you exercise, do you still only consume 500 calories? Or is 500 your NET total goal? For example, if I burn 300 calories through exercise, do I consume 800 for a total of 500 (800 – 300)? Or do I still only consume 500, for a net total of 200? I only have a few pounds to lose, and am only concerned about diabetes because of family history (everyone either has it, is pre-diabetic, or is at high risk, plus high blood pressure and heart disease).

    • Penny Hammond August 18, 2013, 2:59 pm

      According to the book authors, you should stick to 500 calories for women, 600 calories for men on fast days, even on fast days when you exercise – you don’t take into account the calories spent in exercise.

  • Kimberly August 22, 2013, 8:03 pm

    Penny, thank you for all your responses! It’s been almost 3 weeks of 5:2 and I’ve been playing back and forth on the same 3 lbs. Not completely discouraged just yet, but was wondering if even though the pounds are not coming off as I’d hoped, is it possible I am losing inches? I am now strictly sticking to 500 cals, and not exceeding 2000 cals on off days and drinking plenty of water/tea (no sugar/cream). Haven’t received the book yet, so was wondering if they’d mention anything about inches. Thanks for your time!

    • Penny Hammond August 23, 2013, 7:50 am

      I didn’t see anything about inches in the book.
      The authors talk more about general health and longevity, how intermittent dieting may reduce your IGF-1 (associated with cancer) and switch on repair genes to give you a longer life.

  • Helen September 6, 2013, 12:48 pm

    Mosley discusses glycemic index and glycemic load (pp 71-73) but provides few GI and GL data.
    If you are interested, a useful online glycemic index and glycemic load of a few thousand foods:


  • Gayle September 9, 2013, 7:57 pm

    Hi penny.. I am on insulin and have started this diet with the permission of my doctor. We have had to adjust my insulin on fast days. I have been unable to lose weight on many diets. I have 40 pounds to lose and I am hoping this will work!! I am a little worried when people say they have been on for months with little weight loss! Please reassure!!

    • Penny Hammond September 9, 2013, 9:19 pm

      Hi Gayle,
      A lot of people find that with this diet, they can start to relax after so many years of watching and obsessing over everything they eat – that can mess up your relationship with food.
      You can learn to recognize the actual signs of hunger, which may help you recognize and understand what drives you to foods – comfort eating and other issues.
      You may end up getting nutrition you were missing before – by eating lots of greens or protein on fast days, or by allowing yourself fats and other potentially healthy foods that you may have held back on with other diets. (Just watch out for foods you’re addicted to – eating unlimited amounts of them 5 days a week may not have the right effect!)
      Not every diet works for everyone (as you’ve found out!), but if you’ve been depriving yourself on many other diets you may find that this one is just the right thing for you. I hope it works for you.

  • Jim Nimmo September 16, 2013, 5:10 am

    I started this back in November last yera when I was just over 96kg, way too heavy for my 5’9″ frame. On most fasting days I choose to eat nothing only drink diet drinks and black tea. I am now 85.7Kg. It works

  • janice October 19, 2013, 12:52 am

    Can I still fast for two days in a row for 500 calories a day even if I do not need to lose weight? Will it make my bl go down? Should I still take my meds while doing the 5/2! Luv ya, thanks

    • Penny Hammond October 20, 2013, 8:07 am

      The authors recommend that once you reach your target weight (or if you’re at your target weight), you fast 1 day a week or once every 8-10 days so you can have the anti-aging benefits of occasional fasting. Or if you really want to fast 2 days a week, you make sure that your calorie intake on other days balances out your fast days, by eating more calorie-dense foods. You could try both these approaches to see what works for you.

      Check with your doctor about your meds – if your health is improving they can advise how much to reduce them.

  • Kauser October 21, 2013, 8:36 am

    Hi Penny, I have read the book back to front and have done a few fasts. No big problem. I do have a couple of questions. It is desirable not to have lunch isn’t it? So could I have a light/clear’ cup a soup’ at lunchtime provided it falls within my 500lcals? Or should it be avoided really.
    I must admit it does feel good to fast and has made me aware of what I am eating on the non fast days.

    • Penny Hammond October 22, 2013, 7:33 am

      There are different patterns you can follow of what times to eat – some people graze in small amounts through the day, others have only 1 meal, others have 2 meals.
      Experiment a bit and find out what works best for you.

  • Jonathan November 10, 2013, 6:16 am

    I did this diet.

    I put on weight.

    No – really.

    I did not break the rules. I was ruthless with portioning.

    But I soon realised I was indulging on my 5 days because I felt empowered to ‘eat what I wanted’ so I did. It was the classic trade off.

    My sense [I am no scientist] is that fasting may stall the metabolism. This causes humans to hold onto potential energy as fat – kind of makes sense that our bodies would have ‘self preservation technology’ from our maker / evolution i.e. systems in our bodies that will sense a time of famine approaching and then hold onto everything we can get to sustain us – I am guessing winters were pretty tough for most stone age folk…

    My very strong fear is that many folks who do the 5:2 like me will end up fatter [and miserable 2 days a week]

    I get and want the health benefits of fasting but I think metabolisms need fixing before fasting can work long term.

    I am having significantly better results with Fast Metabolism diet which is horribly complicated but once you get it – it is a terrific answer for those of us who eat too much for whatever reason. I do and am changing my body [lots of kilos missing] but also my perceptions of foods: chocolate is a wonderful joy but it isn’t for every day or every week. Alcohol is delightful but is a treat not a coping strategy. My fear for many is that underlying issues which cause obesity [e.g. Carb / Booze / Insulin fuelled excess upon excess binging is almost allowed on the 5:2 whereas it should be highlighted as the cause.

    Be careful


  • Shirley November 14, 2013, 4:12 am

    There was an article about the diet published in The Sydney Morning Herald and a dietician did a menu planner making it easier, so I thought I’d try it. I think I may actually have gone a bit over the 500 calories for a woman but I was’nt going to stress over that as it was just a beginning and much less than I normally eat.

    They said not to weigh all the time so I did’nt bother but after a couple of weeks I had dropped about 4 lbs however I found I got rather constipated. I resorted to 4 prunes at lunch on the next fast day and drank Unique water with all it’s minerals. Then we went on holiday and I did the Monday fast but gave up for the rest of the week – hey, life is short and this was about having fun!

    When we came back I did another week but then got a cold sore – am wondering if it was caused by body being suddenly in a weakened state again. So I have’nt gone back on it until this clears up. I did feel rather weak at around 4 p.m. on the fast day. I don’t know if this is a No-No! but I had chicken, brown rice and salad for dinners and that got me through the night. What bliss the next day to have a normal breakfast but I found I felt fuller and tried not to eat if not hungry on the off days – had the tum shrunk? My question is this: When I go back on the fast can I have a multivitamin to make sure I don’t crack along the way?

    PS: I am 63 (rather an old boiler!)

    • Penny Hammond November 14, 2013, 8:07 am

      Hi Shirley,
      We only look at the food side of diets, not supplements. A lot of people seem to be taking multivitamins on this diet, if you look at the forums on http://www.thefastdiet.co.uk/.
      Good luck!

  • Onka November 16, 2013, 3:00 pm


    Please tell me if this is normal. I’ve been following this diet for almost 2 months, eating close to but less than 500 calories 2 non consecutive days a week (mainly egg whites, chicken, tiny bit of olive oil and vegetables) and eating anything with no restrictions 5 days a week (pizza, cheeseburgers, ice cream etc), and I have gained 24 pounds. I think this is because I am eating whatever I want on the non fast days. Before this diet I was very strict and only ate clean food never exceeding 1,500 calories a day. I was losing weight incredibly slowly and was always hungry and had constant food cravings. Now that I eat whatever I crave and eat until I am full 5 days a week, I keep gaining weight. Is this going to ever stop? Is it because I’m not used to eating junk food?

    • Penny Hammond November 17, 2013, 7:30 am

      Have a look at The 5:2 Diet Book by Kate Harrison Step 1 – pages 96-110. What this book says is that to lose weight, you should have a calorie deficit each week, when you combine the calories from your fast days and non-fast days/feast days. That book gives you details on how to calculate your daily calorie requirement and use it to work out how much you should be eating on non-fast days/feast days. There’s a Chewfo food list for The 5:2 Diet, if you’re interested, but it’s related to what to eat and foods to avoid and doesn’t have the calculations.

      The Fast Diet isn’t meant to be an excuse to eat limitless amounts of junk food… if you eat whatever you crave and are putting on so much weight, you may find some foods addictive. I personally am quite a sugar addict – if I bake a tray of brownies I’m happy to eat the whole lot. So I avoid sugar completely, and fill myself with other foods instead – eating when I’m hungry rather than addictively eating more and more of certain foods even if I’m not really hungry.
      What’s your trigger? Are there any foods that set you off to eat large amounts? For you it might be refined carbohydrates such as sugar and white flour. Have a think about it and see if you can be satisfied with other non-trigger foods without having to calorie-count on your “free” days.

  • Charity December 1, 2013, 6:14 pm

    Jonathan, Onka, and others who have gained weight – I am in the same boat:-( At first i was very optimistic..but the high didn’t last.

    After a few fast days where I kept going 25-75 calories over, I soon was able to follow the diet religiously. Yet I lost no weight at all. Then I read the links Penny provided (for the forum), and cut my calories even more on non-fasting days i.e. from 1700 to 1500.
    Still no weight loss, even a slight gain. I decided to give it another 4 weeks, and cut calories to 1200.

    Imagine my frustration when I not only did not lose weight I gained 6 lbs!! I’m so upset. Needless to say, I’m done w/ the FAST diet. All I can say is I’m so glad it’s not just me; there are others in the same boat. Misery loves company [grin]

    I did find one really great side-effect – on fast days, I felt good, and overall I felt healthier despite no weight loss. I do think it’s messed up my metabolism b/c in just 3 weeks of going off it, I’m gaining weight faster than ever on the same 1450-1500 calorie diet.
    I’m not sure where to go next – alternate day diet has also not worked for me, so now I’m going to try the Fast Metabolism one.

  • Jan April 29, 2014, 10:48 pm

    I can’t speak too highly of this amazing diet. In 4 months I’ve lost Over 8 kilos. I now want to maintain the weight I am, what do you recommend I do now. Thanking you. Jan.

    • Penny Hammond April 30, 2014, 10:22 am

      Congratulations on reaching your goal weight!

      Here’s what the authors suggest for maintaining weight – consider adopting the Maintenance Model: fast on only 1 day a week or once every 8-10 days, or consider adapting your consumption on non-fast days to eat more calorie-dense foods.

  • Jan April 30, 2014, 7:40 pm

    I’ll try this, I’m so happy. Thank you. Jan.

  • Thea May 7, 2014, 3:22 pm

    Hello, I am just starting the fast diet. What is the normal or safe weight-loss to look for? I’ve had people tell me a pound a week, and others tell me up to 10 pounds a week. I don’t know how much is too much. Please help?

    • Penny Hammond May 8, 2014, 7:43 pm

      This book doesn’t make a claim about how much weight you’ll lose, or give guidelines about how fast to lose weight.

      If you’re just starting to avoid sugars and refined foods, you may find yourself losing more than a pound a week. But that’s very short term, while your body is getting used to some dramatic changes in diet – over time, it seems that most people will lose about a pound a week safely.

  • Lydia Jefferies May 11, 2014, 4:56 pm

    Hi, I am a young woman with Asperger’s syndrome and anorexia nervosa, two issues that hound on my life like hailstones.
    I needed to lose weight, and I did something really stupid – I cut my calories too much. I was eating 578 calories, each day, every day. I realised what a fool I was being.
    I am intelligent, well educated, I have studied centenarians and nutrition. I want to live to a hundred.
    So, to cope mentally more than physically, four weeks ago I put myself on the 5:2 diet, with 500 calories on fast days – two days per week- and for the other remaining days, I allow myself 1,200.
    I feel fantastic! When I was on my low diet 0f 578 calories daily, I stopped menstruating and felt week all the time.
    Now I have strength, better mental health and I expect my periods to start again soon.
    I am vegan, but I get plenty of protein and all of my 5-a-day – usually over 10 – and I also get plenty of vitamins!
    What do you think? If I am happy doing this, might it be perfect for me to continue?

    • Penny Hammond May 13, 2014, 7:40 pm

      578 calories a day would cause problems for any adult, so it’s great that you’re now eating more calories.
      There are studies that show that a deprivation diets can extend life in some cases, and intermittent fasts are a way to do it less drastically.

      The 5:2 diet by Kate Harrison suggests that you work out the total number of calories you need per week, and take in consideration both fast days and non-fast days to ensure you’re eating the right number of calories. On average, you’re eating 1022 calories per day. That might not be enough to keep basic functions working – you may need to eat more on non-fast days.

      With Asperger’s syndrome, you may want to try a gluten-free, casein-free diet, which a number of people have found helpful – you’re already casein-free if you’re vegan, but consider trying (unprocessed) alternatives to gluten. If you’re vegan only for health reasons, consider the GAPS diet.
      As you have anorexia nervosa, be careful not to go overboard with dietary regimes – easier said than done.

  • Fasting specialist May 16, 2014, 4:59 am

    This “diet” is based on a fundamental error:
    Fasting means not eating at all, just drinking water and cleaning your colon.
    Insofar the title of this book is misleading.
    On the other hand, lots of followers feel better when they just reduce their calory input twice a week and pay attention to what they eat.
    So just think one step further: if you would REALLY be fasting, even for only 5 or 7 days, how positive this might be for your health?
    From my personal experience I give you some examples what happens after just 10 days of real fasting:
    – Diabetes disappeared and high cholesterol as well
    – No more headache and rheumatism pain
    – weight loss 10 kg (this is not the purpose of fasting, just a positive side-effect)
    – perfect skin (psoriasis disappears)
    – allergies disappear

  • Reg sheen June 7, 2014, 3:55 am

    Hi Penny, can you tell me if it is ok to have porridge for breakfast on the two fast days. Does porridge contain carbs?



    • Penny Hammond June 8, 2014, 1:39 pm

      Hi Reg,

      Porridge is mostly carbs. Some people find that carbs aren’t a good idea on fast days because they contain a lot of calories and tend to make you hungry later; however the book does have a menu for steel-cut oatmeal for breakfast on one of the fast days. Keep the portion size in tight control and see how you react to it on a fast day.

      There are breakfast ideas for fast days in the diet book and cookbook, such as cottage cheese with pear and fig, boiled egg with grapefruit or other low-sugar fruit, smoked salmon and low-fat cream cheese on Ryvita, strawberry smoothie.

  • Ben July 1, 2014, 3:15 am

    Hi. I am a Muslim. I would just like to ask if this method was derived or inspired from the Sunnah (way of Prophet Muhammad (s.a.w.)) in the religion of Islam. We get blessings by fasting during Mondays and Thursdays. Im not trying to prove anything with my question, Im just curious. Thank you.

    • Penny Hammond July 1, 2014, 5:29 pm

      Hi. There are a number of regions and traditions that include fasting, but I don’t think that this diet was derived from or inspired by any of them.
      It’s possible that religions and traditions encouraged the use of fasting because it is a natural cycle that is good for health.

  • Hope July 10, 2014, 3:54 pm

    I have been on the 5:2 diet for about 2 months, with 1 week off while on vaca… I have not weighed myself and will not for a while… This is how I was told by my doctor… Eat dinner, next morning eat 500 calories, mine is an all fruit smoothie with fresh squeezed OJ and cup of coffee with creamer, skip lunch, then eat dinner at the same time that evening you did from the night before… There is your 24 hours… Example…. Dinner at 7pm, 500 calorie breakfast, then dinner at 7pm…7-7 or 8-8, however it is best for you to split the 24 hours…

  • Jose July 19, 2014, 6:10 pm

    Thank you!

  • Angela September 23, 2014, 6:13 pm

    I’ve only just started the 5:2, today is my first fast day. I generally don’t count calories but did yesterday to make sure I wasn’t over 2000 allowed calories and I was way under at 1400. I don’t enjoy take away or sweets on a regular basis so don’t want to consume them just to get my calories up and I was satisfied eating the 1400. My question is if I only consume around 1400 on eat days will this negatively affect my weight loss? I’ve got about 5-7kgs to lose.

    • Penny Hammond September 28, 2014, 2:22 pm

      If you’ve been a long-term dieter and you’re just used to having low calories all days, adding in fast days on top of an already restricted diet probably won’t help you much. Non-fast days are “eat what you want” days – if you’ve had a low-fat diet for some time you may feel like adding in a bit more fat, for example.

  • Kerrie Chapman September 28, 2014, 2:32 am

    Hi there. On fast days the book says to not to put any milk in your tea or coffee yet it seems to be ok to use no fat / low fat milk on your oat cereal. If I have, for instance, a soft boiled egg instead of cereal on a fast day, is it then ok to have a cup of tea with a tiny bit of milk in it (taken with a meal so it doesn’t come under the “grazing” principle)? Also, is stevia allowable in my tea (its not artificial and only has 0.4 cal per tsp – I only use 1/4 tsp in my cup of tea), or is that a no-no as well?
    Last question, my hubby wants to go onto the diet to improve his long term health and brain function. However, he is lean (175cm, 58kg) and loses weight easily (so lucky). With a BMI of 19, would it be safe for him to to go on the “maintenance” diet or is he simply just to skinny? He had his bloodwork done recently and his general health seems to be good overall.

    • Penny Hammond September 28, 2014, 3:21 pm

      In Chapter 2 the authors say “Remember that tea and coffee should be black and sugarless.” I think they’re trying to ensure that what you’re drinking is really just a drink to quench your thirst, not a source of calories. You might be able to have milk with your food, but they seem to treat drinks as something different.
      In general the book recommends “real” foods for the fast days. Stevia originally comes from a plant, but there’s quite a lot of processing involved to create the powder or liquid you put in your tea, so avoid it if you can on fast days.

      The authors of the book are pretty skinny now, but they continued to include fasting days for health reasons. If your husband loses weight easily, he might want to consider eating more on non-fast days to balance out the fast days so he doesn’t lose weight.

      • Kerrie Chapman September 28, 2014, 6:13 pm

        Thanks for the advise, Penny.

  • Kerrie Chapman September 30, 2014, 10:05 pm

    Just letting everyone know (particular for those living in Australia) that Aldi supermarkets sell a variety of potato called Kestrel which is low G.I. (per 100g – 59 cal, 11.8 carbs, 0.2 g. sugar). Probably still not recommended for fast days because of the starch (?), but maybe a healthier spud for the non-fast days. Better still, they’re a great tasting potato and are a good all-rounder for cooking (baking, mashing, steamed etc.).

  • Gerry March 24, 2015, 4:19 am

    I i am in to my second week i have lose 2kg per week i do monday tuseday 75grams fish tins brecky
    p.s.i must menson i am 140 kg when i started.

  • Bryan Kirby July 24, 2015, 12:06 am

    I have been on the 5:2 or 2:5 for 10 days now and my weight is like a yo yo. I lost 1.3kgs and 2 days later I had put it on. Maybe it is too early and I will have to wait a month for things to settle down. Or it could be fluid related. I have got a big bike ride in March of next year and I need to drop at least 10kgs.

  • Darren Glover July 24, 2015, 7:22 am

    I eat a very healthy diet on non fast days.I find it easier not to to eat at all for about 30 hours.I do this once a week to maintain my weight.Do you see any problems with this routine.I don’t get hungry on my fast day
    Thanks Darren

    • Penny Hammond July 24, 2015, 6:43 pm

      Hi Darren,
      There are lots of different patterns that people use for fasting – if this works for you, stick with it!

  • Jan August 10, 2015, 1:19 am


    I have been on the 5:2 now for 13 months and have lost 10kg and hoping to lose a few more. The weight loss is much slower once you are getting close to your goal weight. This has been a flexible and sustainable way to lose weight. I am just wondering if there is a recommended maximum period of time to be on the 5:2 before switching to maintenance mode?

    • Penny Hammond August 10, 2015, 6:26 pm

      Hi Jan,
      The book says to move only maintenance mode once you’ve reached your target weight or just under.
      I can’t find anything in the book that says the maximum time you should be in full intermittent diet mode.

  • Tahmina Ahmad August 19, 2015, 6:39 am

    Hi Penny,
    Thanks for your hard work for our benefit.Would like to share my thoughts. I am really amazed to know about this fasting diet system….you know why? My religion is Islam and as Muslims following the footsteps of our Prophet Muhammad (PBUH) we are supposed to fast on Mondays and Thursdays of every Week to stay healthy and to get God’s blessings.The month of Ramadan is manditory to fast for the whole day for the month.Our diet is also protein-veg based during the month.We start fasting having a meal early in the morning, before sunrise and break our fast during dusk just when the sun starts setting.Our menu is mainly based on chick peas(vegetable protein),salads,veggie and lentil fritters,mixed lentil curry with meat( a mixture of veg & animal protein)lots of fruits and drinks or smoothies made out of lemons or yogurt or other fruits.The most amazing thing is we (muslums)were taught to practice this 1400yrs ago and science is finding out the benefits of fasting only in recent days.But I am happy that I am getting the scientific explanations about it which I didn’t know much before and kept following it from the religious point of view but this Ramadan (just completed few days ago) I enjoyed my fasting in a different way for the whole month knowing all the benefits as I read some articles by prof.Longo on fasting .I kept thanking the Almighty for having these provisions for us as religious rules but is actually for the benefit of mankind. week for goid health though it is optional

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