Looking for the fastest way to find out about 5:2? Look no further! Click on the questions below to find out all you need to get started (but do remember to talk to your doctor before you start any diet, especially if you have an ongoing medical condition like diabetes).
Once you’ve got the basics, learn more about the books that are inspiring people all around the world.
The 5:2 diet involves restricting your calorie consumption to 25% of your energy (calorie) needs, two days a week, and eating normally the rest of the time. This means you’re consuming less calories – so you will lose weight.
Plus there’s a health bonus – intermittent fasting – the general term for these kinds of diets – is thought to help your body repair its cells, which may help prevent diseases including heart disease, stroke, Alzheimer’s and other forms of dementia, type 2 diabetes and cancer.
Many people also report improved results in health tests like blood pressure and cholesterol testing, alongside significant, and sustainable, weight loss.
For many of us, the fasting days also make us much more aware of what we eat all the time, so we make healthier choices and savour every meal. Increased energy and a feeling of freedom from cravings and anxiety around food is also really common.
No – you never have to go a day without food. We simply use the term Fast Days to describe the days when we limit our food intake to a quarter of what our bodies need. The average limit for women would be 500 calories, with 600 for men (though you can calculate your exact numbers right here).
That limit allows you to eat small meals up to three times a day. Some people do end up fasting completely once they’re used to 5:2 but you don’t have to do that.
In theory, you can have whatever you like – so long as it stays under the calorie limit.
But to keep hunger pangs at bay, it makes sense to eat smartly. Focus on foods that are naturally filling without too many calories, and that keep you feeling fuller for longer. Choose:
You can eat up to three times a day, though the meals will be small. Some evidence suggests the health benefits may be greater if you stick to one or two meals. So that could mean any combination of breakfast, lunch and dinner. Many of us now skip breakfast – or lunch – and it feels a very easy part of our routine.
See What can I eat on a Fast Day for more information on planning your 5:2 days.
Most people find it easier to split the days up (so they might fast Monday and Wednesday rather than Monday and Tuesday). That's because the hunger pangs can be stronger and a two-day Fast can be tougher when you’re starting off.
But it can be more convenient to do ‘back to back’ fasts, so long as you don't exceed 48 hours. Also, don't forget you can pick different days to fast to suit your plans each week.
People who should avoid fasting include pregnant women or nursing mothers, children and teenagers, and those with a history of eating disorders.
Those with Type 1 or Type 2 diabetes, or other chronic or acute medical conditions must talk to their specialist before embarking on this plan. It always makes sense to check with your doctor before any lifestyle change so they can advise you.
No – unless you’re in one of the small groups of adults who should avoid fasting (see the question Who shouldn’t fast?), then cutting back twice a week isn’t harmful, in fact, the evidence suggests it helps the body repair itself. Our ancestors evolved to thrive on a pattern of fasting and feasting – and we can too.
Current research on intermittent fasting – the general term for diets like 5:2 – suggests that the approach is at least as effective as ‘normal’ dieting. Further research is investigating potential benefits in terms of blood sugar, and the ‘inflammatory response’ in the body that is a factor in many medical conditions, including cardiovascular disease, cancer and dementia.
On first fast days, people often expect to feel really hungry. But thought you will be aware of eating less, you’ll probably be surprised at how quickly any pangs pass, especially if you keep busy with work or other activities. On the first few fasts, some people report feeling the cold more, or experiencing headaches – both of these are common with all diets. Most people find it gets much easier after the first one of two fasts.
Intermittent fasting is safe for most people, but on the first few times, it’s worth keeping a small snack handy in case you do feel unwell. If you do feel faint – which is very rare – then don’t hesitate to eat something, and talk to your doctor before trying it again.
This has a simple answer, and a complicated one.
The simple answer is: yes, you can eat what you want – including favourite foods - on normal days, without calorie counting.
BUT… ‘eat what you want’ isn’t the same as ‘eat as much as you want all the time.’ Fasting for two days a week will cut the calories you’re eating by around 3,000-3,500 (equivalent to about a pound a week of lost weight) – but if you overeat a lot on the other days, you can cancel that out.
Most of us find that bingeing doesn’t happen and that we naturally eat more mindfully on normal days, because we savour our foods and we also have a much better idea of how much we need to eat to satisfy our appetite.
The trouble with calorie counting is, it’s boring. But if you feel you do want to calorie count on normal days, then you can find out what your body actually needs (known as your Total Daily Energy Expenditure) via this calculator. If you’re used to traditional every day restricted diets, you’ll be pleasantly surprised!
Many of us do exercise while fasting, with no ill effects. It may be a good idea to avoid very vigorous exercise until after your first couple of fasts – and if you feel unwell, then listen to your body and stop.
One thing to note – you shouldn’t add any calories burned through exercise to your calorie allowance on a fast day – stick to 500-600 for the health benefits!
Dieters in our groups have lost anything from a few pounds/kilograms to over six stone/38 kilograms.
It’s a good idea to weigh yourself before starting (and then again at the same time each week), and also to take chest, waist and hip measurements. The rate that you’ll lose depends on your age, levels of activity and your own body – so don’t be disheartened if you’re losing a pound a week while others are losing five or more. Typically weight loss will be faster at the beginning of the diet, and for those with a lot of weight to lose to reach a healthy weight (see this calculator to find out what a healthy weight - or BMI - is for someone of your height and weight).
The important thing about 5:2 is it’s very sustainable – and you’re more likely to be able to maintain the loss.
Weight loss does fluctuate – try not to weigh yourself more than once a week at the same time, and bear in mind that hormones and digestive processes can affect our weight by several pounds – even if we are losing fat.
But if you go for more than three weeks with losing weight, try these ideas:
No - you can vary the number of days, to suit you. We call it 5:2 but you can try 4:3 – with 3 fast days – which may speed up weight loss. ADF means you fast on alternate days, while 6:1 is how many people maintain their weight loss.
Many of us hope to stay on 5:2 for life, because it feels so easy and natural. Once you reach a healthy weight, you might like to shift from 5:2 to 6:1 – again, it’s your decision. Certainly, the health benefits mean it's a plan that can offer more than weight loss alone.