The intermittent fasting diet, also known as the Horizon diet or the 5:2 diet (because you eat what you like for five days and fast for two) provoked huge interest when the reporter Michael Mosley reported his findings on its impact on weight loss, health and longevity on BBC 2's Horizon last year.
Michael has now produced a book, The Fast Diet (all this diet needed was another name) based on his findings and kindly agreed to answer gransnetters' questions on how it works - and how quickly we're all going to end up with bikini bodies (we can dream...)
Q: I have several friends on this diet and it really does seem to work for them. Can you please tell me if it is necessary to consume 500 or 600 calories per day and does it have to be on consecutive days to have the maximum effect? I am throwing everything at losing 5lbs in the next month. I walk 40 mins everyday and play badminton 3 times a week and watch my diet carefully. Do you think it would be possible to achieve this on the fasting diet? I am 66. robbo
A: The scientific studies are based on men consuming 600 calories and women 500 calories, so that seems a reasonable guideline. Clearly if you find that difficult you can increase, but you won’t see so much change. I do it Mondays and Thursdays, you can choose which days you want. Doesn’t matter if consecutive or not. On this you should lose around 1lb of fat a week; the apparent weight loss will be more because you will also lose water. Drink loads on fasting days.
Q: I have type 2 diabetes. Will this diet be suitable for me? Murphymycat
A: Best talk to your doctor.
Q: I have tried fasting on some days (for health reasons rather than weight loss) but I wake up in the night and am unable to get back to sleep because I am so hungry. Unless I get up and have a bowl of Greek yogurt and honey, or some such, I can't get back to sleep. Does this suggest that going hungry probably isn't good for me? (It certainly isn't good for my work rate the next day!) icabodisitchy
A: Try changing your pattern so you have a bigger meal in the evening or put aside a few calories for a glass of milk, which can be filling.
Q: My husband and I are on our second fast day and are finding it surprisingly easy.Before I reached the menopause I didn't have a weight problem; if I put half a stone on I just ate less and exercised more and within a couple of weeks I was back to normal. When I reached the menopause, this weight stabilisation pattern ceased to work and over 15 years I gained 2 stone despite constant endeavours to lose it. In my mid 60s my weight stabilised and I have actually begun to lose weight but it has taken over a year to lose a stone. Is there any evidence of the effectiveness of this regime with older/post-menospausal women? FlicketyB
A: A number of studies have been done which have included pre- and post-menopausal women and both seem to have done well.
Q: I started the routine which worked very well for me until Christmas at which time I gave up. I am about to start again but I do wonder how healthy fasting actually is when we are continuously told not to allow blood sugar levels to fall too low and to eat little and often. My problem seems to be that once I start eating I carry on with gusto and feel hungry all day whereas if I don't eat at all until the evening, I don't have even the slightest hunger pang. Labouroflove
A: The idea that you should eat little and often to speed up your metabolism or prevent your blood sugar levels falling is largely a myth. There have been quite a few studies that have shown no difference in metabolic rate between those eating their daily calories split into three meals a day or six. Your body is extremely good at maintaining your blood glucose levels and there should be no problem, unless you are a diabetic. You would need to fast for over 60 hours to have a serious impact on blood sugar levels.
Q: I love the idea of it, but wonder how you manage to stick to it on the "fasting" day? Whenever I restrict my intake, I get so hungry that by dinner time, I would eat anything. Where do you find the willpower? hummingbird
A: I find the main thing is to have a protein rich breakfast (protein is satiating), lots of fluid during the day and lots of vegetables in the evening with, say, a slice of meat or fish. What you want is bulk and protein, those are the things that keep you full. If you find you can’t do 500 calories, try 600.
Q: Does this way of eating work for vegetarians? I have not eaten meat or fish for 30 years. Would one still get enough nutrients eating this way, I wonder? waterlily
A: Works well for vegetarians because they already know the secret of feeling full in filling up on veg.
Q: I have very easily lost 2.5 stone since seeing your Horizon programme, with alternate day fasting, but for the last month I have reached a standstill, although I still have some to lose. Do you know of any change in regime which could kick start the loss again? This diet has been so easy to follow and I am happy to continue for as long as it takes. Shysal
A: Look at the fluids you are drinking on your "feast" days. Fruit juice, smoothies, lattes and booze are all calorie rich and are not satiating.
Q: Is this about weekly calorific intake plus the idea of keeping up the metabolic rate? I seem to remember something similar by an American ten years or so back. It sounds very "doable", the five days would be no problem. Are there rules for the five day bit or is it anything goes? Sel
A: If you want to know the rules and the science read my book, The Fast Diet, or google some articles I have written.
Q: I started doing intermittent fasting last summer and found it easy and very flexible. I lost weight steadily and easily and can't see why I shouldn't eat this way forever. However, I thought at first that the limit was 600 calories a day and it was some weeks before I discovered that was just for men! As it had been working well, I didn't bother going down to 500 calories. As long as I keep busy, it's fine. ?So, as I'm over 60 and reasonably active, is it ok to go over the 500 calories? I feel there ought to be some leeway for an older person! ?Also, is there any more info on the maintenance phase? I've got your new book, The Fast Diet, and it says one day a week is fine, but are there any other tips? WinterGran
A: You seem to be doing just fine and as long as you are feeling good I wouldn’t get pre-occupied by numbers. This is all about finding something practical that works for you.
Q: I really enjoyed your programme about the gut. Quite brave subjecting yourself to being a lab rat in front of a live audience and TV cameras. But was it really that painful having the balloon thing inflated in your oesophagus or were you playing up for the cameras? JessM
A: It was extremely painful but also extremely interesting. Who knew that introverts react to pain so differently to everyone else?
Q: Firstly - are the fast days 500 or 600 calories? Opinion seems to vary and you can get a whole lot of ryvitas in for that extra 100 so it makes a difference! And secondly - do you have tips for coping on the "fast" days? I can imagine getting to lunch time and giving in! leila
A: Broadly it is 600 for men and 500 for women. If you want tips for coping, best join a 5:2 group or thread. Plenty on Gransnet.
Q: Is it really true that people don't binge on the days when you can eat what they like? I am sure I would be stuffing myself after the abstinence. And then I start wondering how you can possibly lose weight if you are eating - say - a Mars a day 5 days a week. lunaballoona
A: Dr Krista Varady, who has run a number of trials, found that people thought they would binge but in reality didn’t. I certainly find I eat no more than normal or "feast" days.
Q: Please can you tell me if there is a "best" way to space out the two fast days? marika
A: No, no “best way”, whatever suits you. I do Monday and Thursday.
Q: I read in the Mail last week that My Fitness Pal is the best method of losing weight because it's based on the (fairly obvious) principle of eat less, move more and pretty sustainable - unlike diets that, say, cut out entire food groups such as carbs and then as soon as you start eating "normally" the weight piles back on. So how does the 5:2 compare (in terms of results and sustainable lifestyle choices) to, say, eating 1200 calories a day and "earning" extra calories by exercising? fruitloop
Q: I am following a low calorie diet of approx 1200 calories a day and although it was fine when I started it seems to be getting harder rather than easier as I had expected. The plus side is that it has really made me think about what I eat. The minus that I am permanently ravenous. So part of me now thinks that your diet couldn't be any worse than this - and part thinks if I feel this bad on 1200 calories how the hell will I cope on 500 - even if it is only for 24 hours? cathymcd
A: Try it and see. A recent study done by Dr Michelle Harvie at Manchester University found that volunteers on a 5:2 diet, when compared to those on a more typical 1200 calorie a day diet, were more likely to stick to it, lost more weight and had improved biomarkers.
Q: Why are the number of calories you can eat on the fast day based on gender and not weight? My daughter is only an inch taller than me but weighs considerably more - yet has the same calorie allowance as me rather than the same as her father who is much closer to her in weight and has proportionally less weight to lose. FlicketyB
A: It is just a guide. If you want to eat 600 calories that is fine; weight loss will be slower.
Q: I would like to ask about non-fast days...as the recommended intake for a woman who is not dieting is 2000 calories, would it be wise to try to stick to this on the days you can "eat what you like" - assuming if you just stuff yourself with no heed to how much you are taking in the weight will be harder to shift? rosiemus
A: Yes, better to stick to your normal intake rather than try to stuff yourself.
Q: I'm going to fast for Lent. 40 days. Fasting is not just a religious thing, it is built in to our natural systems. Our ancestors were not able to rely on a quick trip to the (super)market and so expected to eat for a few days and then not eat again for a while. Fasting is good for the soul and probably even better for the body. In Germany this is taken very seriously. But the big problem I face is eating from boredom! So how to alleviate boredom - not just with what is on the plate, but using food as a comfort? Brabant
A: Sorry, I don’t have an answer to that. Cultivate interests, walk, do something unexpected for someone else.
Q: Lost 6lbs in two weeks before Christmas but put 5lb back on over the dreaded festive season. Nothing daunted I started again on Jan 3rd and am losing about 1.5lbs per week. This diet is good for me because it is not relentless. I don't find it difficult to keep to the 500 calories on fast days as long as I don't start eating til about midday. My question is this: will my all-knowing metabolism twig what I am up to eventually and slow to a standstill on fast days? muswellblue
A: As we lose weight our metabolism slows simply because we are carrying less weight around. So you will find weight loss slows, but hopefully not until you reach your desired weight.
Q: Husband and I have been doing this since the programme went on air - we fast two days a week.So far nothing but benefits, being slimmer, and more alert. Many of my friends and associates are doing this too. Is there any value in setting up a national clinical trial to determine the savings to the NHS, and the benefits to participants, of doing this on a long term basis? A bit like the Million Women study by Prof. Beral? With regular measures of cholesterol, blood sugar, well being etc. Can I be the first volunteer! JacquiG
A: I think that is a splendid idea but unfortunately I don’t have the time or resources to carry out such a trial.
Q: My husband needs to lose a lot of weight but may have post-operative anaemia so is the fasting diet suitable? Bay
A: Best to discuss with his doctor.
Q: Is there really any advantage to any of the fad diets as opposed to just eating more sensibly? The problem for most people in affluent countries is they just eat far too much, and a lot of that is heavily processed food. I believe the recommendation for a woman is 2000 calories a day, so wouldn't it be a better idea to reduce your intake to that, or even a little less? The online guides to calorie counting are full of assumptions, but I've just done a count of what I have eaten and expect to eat today and got less than 1000. I have no intention of following the "crash diet then binge" route though. MaryXYX
A: Eating sensibly is clearly a good idea; the problem is that people find restrictive diets hard to stick to. As I mentioned above, a recent study done by Dr Michelle Harvie at Manchester University found that volunteers on a 5:2 diet, when compared to those on a more typical 1200 calorie a day diet, were more likely to stick to it, lost more weight and had improved biomarkers.
Q: Have been doing this eating plan for a week and found the fasting days somewhat difficult. However I was fasting for a day and a night. Have read that you can fast for 24hrs, so from 2pm one day to 2pm the next which would seem far more manageable? scarlet
A: Try experimenting and see what works for you. We are all different.
Q: I did the plan till the end of November and felt good, losing half a stone, I've now restarted. My problem: It's too hard not to over-eat once I start so I load up the calories at the end of the day, eating at 7:30 in evening. But I do feel very light-headed and find it hard to concentrate by that time. Is it dangerous and do you have any tips? jandrew
A: Best join a 5:2 group for support and tips.
Q: I've just started an NHS weight loss programme, and they're advising a very complicated calorie controlled diet. Is the NHS considering advising the fasting diet? maxine
A: I think they are awaiting the results of more human trials.
Q: I read an article in the Guardian about the Fast diet by Hugh Fearnley-Whittingstall as he's been on it post-Christmas. This is followed by a piece by Dr Luisa Dilner, regular health columnist, who says this diet is not suitable for people with diabetes but does not say why - so what is the story? Cerasus
A: Diabetics have more problems controlling their blood sugar levels and need closer supervision.
Q: Does size matter? I am 6ft tall (and 73 with arthritis). I tried the diet before I went on holiday last October and felt utterly miserable on my low-cal days, began to dread them. BarbaraAbbs
A: If you found you couldn’t cope then this is not for you. Normally after a couple of weeks people adapt.
Q: My wife and I have been on the 5:2 diet for about two months with fairly good results. However we wonder whether we would see better weight loss if we did not eat the 500-600 calories on our fast days. Am I correct in thinking that the researcher you interviewed about intermittent fasting said that ideally one should not eat anything on fast days? In other words, is the suggestion that you can eat a small amount on fast days merely to make the diet easier to sustain? Also, is it likely to be more effective to fast on two consecutive days to really switch on that fat burning mode? goodtogo
A: Eating calories on fast days is partly because it is easier to sustain but also partly to keep up levels of nutrients and protein. Protein is not well stored and needs topping up every 24 hours.
Q: I am a bit puzzled about the fast times. I start the fast after supper and following your guidelines eat around 500 calories during the following day and end the fast with supper. That means I eat my main meal on both days with snacks in between. It seems to me that isn't much of a fast. elizabethb
A: Fasting means abstaining from eating for varying lengths of time. I aim for 12 hour stretches, but others find that tougher. Research by Dr Michelle Harvie, cited above, suggests that reduced calories twice a week, even when spread throughout the day, brings significant health advantages.
Q: I read somewhere that the reason people in Yokohama live even longer than the generally long-lived Japanese is that their culture dictates that they leave the table when they are 90% full. Is this another way to come at it, or do you need the on-days/off-days to have the effect? sneetch
A: It is another way of coming at it.