So how do I do this fasting thing?
What if I’m not average? How do I know how much I can eat?
Do the days have to be consecutive?
Do the 500/600 cals have to be spread across the day or in 1 meal?
How long is a fast day anyway? I've heard people talk about 24 hours or 36 hours, I'm confused!
Are there any rules about what I should eat on a fast day?
Are there any rules about what I should drink on a fast day?
Is it OK to have Diet Coke or similar drinks?
What should I eat on my non-fast days?
Should I count calories on non-fast days?
Can I exercise on fasting days?
Can I increase my fast day calories if I exercise?
How can I expect to feel when fasting?
How can I stop the headaches/feeling shaky?
Should I fast if I am unwell?
How much weight will I lose?
How should I monitor my progress?
How often should I weigh/measure myself?
I've not lost any weight! What have I done wrong?
How do I know whether my risk of heart disease, diabetes, etc has improved?
Is fasting safe for everyone?
I’ve heard that not eating at least 3 meals a day is bad for you, so surely fasting is bad?
I’ve been told that fasting will cause my body to enter 'starvation mode and hang onto fat?
Can I fast more/less often?
I hear that protein intake should be reduced, is this true?
What about carbohydrates?
I’ve heard about something called IGF-1 that is supposed to be important…what is it and can I get tested for it?
Where can I watch Dr Mosley’s Horizon programme about fasting?
Where can I buy Dr Mosley’s book?
Are there other forms of intermittent fasting I could try?
Q: So how do I do this fasting thing?
A: Basically, you eat normally (but not bingeing) on any 5 days of the week and then fast on the other 2 days. On the fast days, you drink plenty (water, green tea, herbal tea, black tea, black coffee etc) and you may consume up to 25% of your recommended daily calorie intake (for the average woman that is 500 cals and for the average man, 600 cals ). Normal eating means normal for your height and weight, if you're not sure what that is, see below!
Q: What if I’m not average? How do I know how much I can eat?
A: If think you are not average (i.e., shorter/taller/more active) you can use this total daily energy expenditure (TDEE) calculator to work out your recommended intake for non-fast days, and divide that figure by 4 to get your fast day allowance. Or, better than that, register with our progress tracker which will give you an estimate of your TDEE, updated each time you enter a new weight!
Q: Do the days have to be consecutive?
A: No, in fact, most people split them up (for example, Monday and Thursday). Choose whichever days fit your life that week.
Q: Do the 500/600 cals have to be spread across the day or in 1 meal?
A: It’s up to you. Dr Mosley split his between breakfast and dinner, but most people prefer to save their calories for a good sized evening meal. No one yet knows whether there is any health advantage to saving up the calories for one meal.
Q: How long is a fast day anyway?
A: Wake up, eat up to 25% of your normal calorie intake (usually 500 for women, 600 for men) at any stage before you go to bed that evening and then back to normal eating the following morning. There is no need to think about what time you ate the day before and start counting the hours or what time you will eat the day after. If you want to alter this for your own reasons, then you can as the keystone of this diet is flexibility. Be aware, however, that you may end up not cutting your overall calorie intake very much, which will slow your weight loss.
In the Fast Diet book, mention is made of 'fasting' 24 hours e.g. from 2pm to 2pm. This has caused a lot of confusion. The problem is that if you eat a big lunch before 2pm, eat 500/600 cals over the next 24 hours and then have a big lunch to break your fast at 2pm, the calorie restriction will be so small that there are likely to be very few benefits in terms of weight loss. If you wish to follow this idea, it is worth sitting down with a calculator and working out whether you would be decreasing your weekly calorie intake by at least 3000 cals. Less than this figure is unlikely to result in any weight loss (1lb of fat is worth 3500 cals).
Q: Are there any rules about what I should eat on a fast day?
A: No! However, if you use up your calorie allowance on high calorie/high carbohydrate foods (beware that some fruits are surprisingly high) you will likely feel much more hungry than if you have few carbs and fats, only moderate amounts of protein and lots of vegetables. But, whatever works for you is the right way to do it!
Q: Are there any rules about what I should drink on a fast day?
A: Again, no rules, except that you need to drink a lot or you may get headaches. We normally get a lot of water from food so if you are not eating you need to drink more to compensate. Naturally it makes sense to drink things that are no/low cal. If you drink a lot of tea/coffee with milk you will need to take the calories in the milk off your fast day allowance.
Q: Is it OK to have Diet Coke or similar drinks?
A: There is a long thread here about whether diet drinks are a wise choice. Dr Mosley has said he is against them but please review the thread on this if you are going to be having a lot of diet drinks.
Q: What should I eat on my non-fast days?
A: You should just eat normally. Many people find that their appetite is reduced and that they tend not to crave 'junk' foods. This helps to ensure you don’t overeat on your non-fast days.
Q: Should I count calories on non-fast days?
A: There should be no need to count calories except on fast days. One of the best things about this way of eating is that you don’t have to be on a diet at all for 5 days a week. Some people do count calories – either for interest or because they are afraid they may over-compensate on feed days. Actually, after a while the decrease in appetite that comes following a fast means that over-compensating is less likely.
Q: Can I exercise on fasting days?
A: Yes! In fact, exercise on fast days will help use up the fat stores and some even say they have more energy. However, it is probably unwise to attempt endurance events, such as running a marathon! Please ensure you keep hydrated.
Q:Can I increase my fast day calories if I exercise?
A: No, I'm afraid not. Your fast day calories are based on being a quarter of your normal daily calorie requirement (how many calories your body normally burns), this already takes account of your exercise. If you do a lot of exercise you need to work out your total daily energy expenditure using this calculator to work out your recommended daily intake, and divide that figure by 4 to get your new fast day allowance.
Q: How can I expect to feel when fasting?
A: We have to be honest and tell you that the first few fasts may be difficult. But it really does get much easier with each fast you do. You will, of course, feel hungry, but this is natural and it comes in waves. Be assured that the hunger does not get worse and worse. The feeling will pass. Having a drink of water, tea, coffee or some vegetable stock/Bovril or similar, will help. You may get headaches, feel a bit shaky or experience some stomach discomfort, especially for the first few fasts. Some people find they are a bit grumpy and irritable at times. You may sleep poorly that night and may feel lethargic the next day. Some people notice changes in their bowel function (both sluggishness and the opposite have been reported)! Some people have experienced smelly breath. However, please be reassured that once you have got a few fasts under your belt, you will likely have very few/no side effects.
Q: How can I stop the headaches/feeling shaky?
A: These feelings are thought to be due either to blood sugar being low (because your body is not used to using fat as a fuel) or to dehyration (or both). Drinking plenty on fast days, avoiding sugary or high carbohydrate foods and drinks on fast days and avoiding loading up with sugar and carbs on the night before the fast may help. It's OK to take a couple of paracetamol (called acetominophen in some countries) to ease the headache during the first few fasts.
Q: Should I fast if I am unwell?
A: Because fasting can affect your immune system (which is good when you have inflammatory diseases like asthma etc), it is probably best not to fast when you are ill. However, best of all is to listen to your body. Sometimes when ill we want to fast naturally, other times we want comfort food. So, it’s best to follow your instincts until you feel better.
Q: How much weight will I lose?
A: Naturally, this depends on how much weight you to need to lose, how active you are and lots of other factors. We have been collecting information from people on how much they have lost. To help us with that, you are very welcome to enter your information in our weight tracker (to be found in the user menu on the left hand side of your screen). Our data so far show that the average weight lost per week is around 1lb (just under half a kilo). If you visit the forum stats tab in the progress tracker you can see how different groups of people are doing and you can filter the data by your own characteristics to see how people like you have got on.
Although some people are reporting big losses particularly at the start, most others are finding that 1lb a week is the norm. Please do not be upset if you do not lose weight fast. We have also created a predictor tool which can estimate how much weight you will lose during your first year of fasting.
Q: How should I monitor my progress?
A: While most people think that hopping on the scales is the best measure of how much fat is going, actually, your waist measurement is the best guide. (Try not to suck your stomach in though, or you will have to carry on doing this for every measurement and do you know how much you sucked it in last time?) Your waist size is a good guide to how much fat you have in your abdomen (the most dangerous place to carry fat) and it is recommended that your waist should not measure more than half your height. Of course, just about everyone steps on the scales too! Be aware, though, that lots of things can affect your weight so you might find you don’t lose weight one week (or even increase) and maybe next week lose several kilos.
Q: How often should I weigh/measure myself?
A: It's up to you! However, scientific studies have found that people who weigh every day tend to be more successful at losing weight and keeping it off. If you weigh daily you will quickly see that your weight fluctuates up and down, apparently randomly, but in fact due to changes in body water content. So, it is important to look at the long-term trend in weight (which will almost certainly be going downwards) rather than the day-to-day variations. The progress tracker will help you to see what is happening behind the variations. If you weigh weekly, remember the day to day variations that are happening in the background and so do not worry if some weeks you appear not to have lost any weight. Again the progress tracker will help you see the long-term trend. The tape measure is probably more reliable than the scales, but slower to show a change, so weekly measurement should be all that is needed.
Q: I've not lost any weight! What have I done wrong?
A: Probably you have not done anything wrong! It is to be expected that there will be some weeks when your weight does not change or even may appear to increase. There are lots of reasons for this (discussed in detail in the forums). The first thing to do, therefore, is to be patient for a couple of weeks (hard, we know)! If you still don't lose any weight, you need to look at whether you are miscalculating your fast day calories, whether you might be over-eating on feed days or even under-eating on fast days. Please post a question in the forum and we'll try to help you get to the bottom of it!
Q: How do I know whether my risk of heart disease, diabetes, etc has improved?
A: Ask your doctor’s surgery to test your blood for the following things: total cholesterol, LDL and HDL cholesterol and fasting blood glucose. Also get your blood pressure checked and have a sample of urine tested for protein. If you can get these tests done before/early on in your 5:2 journey, and again after, say 6 months, this will be give you a good guide on whether you have made a difference to your risk of these diseases.
Q: Is fasting safe for everyone?
A: For most people intermittent fasting should be no problem. There are, however, certain groups who should not fast:
• Pregnant women
• People with Type 1 diabetes
• Anyone suffering from an eating disorder
• If you are already extremely lean.
If you are on medication of any description, please see your doctor first, as you would before embarking on any weight-loss regime.
Q: I’ve heard that not eating at least 3 meals a day is bad for you, so surely fasting is bad?
A: Not at all! Your body has been designed to withstand long periods without food. Fasting has been practised by different peoples for hundreds of years. Followers of the Islamic faith, for example, fast during daylight hours for the month of Ramadan and some also fast twice a week year round. Scientists have not been able to find any health problems associated with fasting for these people. In fact, they have found that the health of people improves during Ramadan with lower cholesterol levels, blood pressure and weight.
Q: I’ve been told that fasting will cause my body to enter 'starvation mode' and hang onto fat?
A: Answer from Dr Mosley’s book: “Since you're not restricting calories every day, your body will not enter the fabled 'starvation mode'. Your fasting will never be intense. It will only ever be conservative and short-lived, so while your body will burn energy from its fat stores, it will not consume muscle tissue. Research has shown that occasional fasting does not suppress the metabolism. Even extreme fasting – an absolute fast for three consecutive days or on every other day for three weeks – generates no decrease in basal metabolic rate. Nor does Intermittent Fasting raise levels of the hunger-stimulating hormone ghrelin. Researchers at Pennington Biomedical Research Centre in Louisiana found that ghrelin was unchanged in both the men and the women, even after 36 hours of fasting.”
Q: Can I fast more/less often?
A: Some people who are looking for greater/faster weight loss have moved to 4:3 (3 fast days a week) and had improvements in the speed of weight loss. If you wish to slow down/stop weight loss of course you can fast less often. Many people fast on a 6:1 pattern for maintenance.
Q: I hear that protein intake should be reduced, is this true?
A: Dr Mosley’s book talks about aiming at a reasonable level of protein and suggests 0.8g per kg of body weight as an ideal. There is some evidence that keeping protein intake to moderate levels will bring many long term health benefits, in connection with encouraging your body to go into repair mode, but this has not been proven. This is the subject of a long thread in the forum here.
Q: What about carbohydrates?
A: It is possible that a diet high in carbohydrates/sugar makes fasting more difficult, with more side effects (e.g., headaches, feeling weak). There is also some scientific evidence that a diet high in carbohydrate prevents the body entering repair mode, but again, this has not been proven. It seems, however, that the fasting process tends to make high carbohydrate foods less appealing.
Q: I’ve heard about something called IGF-1 that is supposed to be important…what is it and can I get tested for it?
A: IGF-1 (insulin-like growth factor 1) a hormone that is involved in many body processes but especially growth. Levels of IGF-1 change with the amount of food eaten. The amount of IGF-1 in the body seems to be higher in people who are overweight and/or who eat a lot of protein and/or carbohydrates. High IGF-1 levels have been noted in people with certain diseases, including some cancers, heart disease and Alzheimer’s disease. People with Laron Syndrome (a condition where they do not have IGF-1) do not develop these conditions. Fasting is thought to help bring high levels of IGF-1 down. Of course, if you are still growing, IGF-1 is a good thing (people with Laron Syndrome are very short), and very low IGF-1 levels often accompany the frailty of old age. Unfortunately, it is not possible to be tested for IGF-1 at your doctor’s surgery. You can pay to be tested, though it is quite expensive (search online for companies offering the test). As no-one actually knows what the ideal IGF-1 level is, the test results do not give you any indication of your risk of developing cancer, heart disease etc.
Q: Where can I watch Dr Mosley’s Horizon programme about fasting?
A: http://www.disclose.tv/action/viewvideo ... ve_Longer/
http://www.dailymotion.com/video/xvdbtt ... shortfilms
There are also rumours (spread by Dr Mosley) that the BBC are thinking of repeating it and/or making an update programme.
Q: Where can I buy Dr Mosley’s book?
A: The book, called The Fast Diet, is available from Amazon: click here
There is also a recipe book click here
And there is a website: http://www.thefastdiet.co.ukamazon
Q: Are there other forms of intermittent fasting I could try?
A: Yes! As well as 5:2 fasting there are other options that you might like to experiment with, perhaps if you have over indulged sometimes or, conversely, when you feel you have lost enough weight and wish to maintain. These are:
ADF - alternate day fasting - in this case you fast in the same way (i.e., 500/600 cal) every other day. This approach has had a lot of scientific research done but may be harder to fit around your life.
4:3 - as 5:2 but with an extra day
16:8 - eating during an 8-hour 'eating window' and fasting for the remaining 16 hours every day (no calories) - in this you generally skip breakfast and then eat normally at your midday and evening meals with no calorie restriction (also known as the '8-hour diet' and 'leangains')
19:5 - as in 16:8 but with a shorter eating window (also known as the 'fast-5 diet')
Eat-Stop-Eat - fast for 24 hours (no calories) on one or two days a week and then eat normally. There is no calorie restriction when you resume eating.