Intermittent fasting is a weight-loss strategy that’s hit the headlines over recent years with high-profile figures such as George Osborne and actor Benedict Cumberbatch said to have achieved results with the diet regime.
Of course, the idea itself is far older, as fasting has been used in different ages and cultures for spiritual and health benefits. Nowadays, intermittent fasting promises to help you lose weight, and is also said to improve blood pressure and cholesterol levels.
But is the practice of eating little or no food for short periods followed by periods where eating is unrestricted right for everyone? And what does it really entail? Here’s the inside track.
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What is intermittent fasting?
Intermittent fasting – including in the forms of the 5:2 diet and 16:8 diet – means swapping a three meals a day or similar pattern of eating for one with brief periods of fasting or low calorie intake, and periods where eating isn’t restricted. It’s different from other diets in that it’s not focused on what you eat (although that is important, see below), but when you should eat.
The idea is that you lose weight because, overall, you’re eating fewer calories. A very low calorie diet maintained over time could also make you lose weight, of course. However, the idea is that by fasting intermittently you prevent the body’s adaptation to a low calorie diet that can mean that you stop losing weight after a while.
Intermittent fasting gives you a formula for when you don’t eat – or, depending on the specific option you choose, eat very little – and when you can eat unrestrictedly. There are different approaches include whole day fasting on some days of the week – for example the 5:2 diet (see below); time-restricted eating with a daily period when meals are eaten and fasting for the remaining hours – like the 16:8 diet (see below); or fasting on alternate days of the week.
Intermittent fasting benefits
Other than potential for weight loss, intermittent fasting is said to increase our resistance to stress, to lower cholesterol and to improve our bodies' blood sugar regulation. It is also said to decrease our blood pressure and resting heart rates.
What is the 5:2 diet?
If you want to try intermittent fasting with the 5:2 diet, you’ll eat normally on five days of the week. On the other two you don’t actually fast, but you only eat a quarter of your usual calorie intake, that is around 500 to 600 calories.
The fasting (low calorie) days shouldn’t be consecutive – so you’d make them, say, Monday and Thursday or Wednesday and Saturday.
What is the 16:8 diet?
Go for the 16:8 diet, and you can eat within an eight hour period daily, while you fast for the remaining 16 hours of the 24 hour day.
You can make the window when you eat whatever time you like, but it’s often recommended that you opt for something like 12 noon to 8pm, or 1pm to 9pm. That way, you’ll miss breakfast but get to eat lunch and dinner.
Intermittent fasting for weight loss
Forgetting everything else for a moment, simply restricting when you eat and cutting out snacks should mean fewer calories are consumed (see below for more on that), which can, of course, aid weight loss. Also, because you aren't denying yourself your favourite foods, except on fasting days, you may feel less inclined to break the diet. However, as discussed below, it's important on non-fasting days to eat a sensible diet – fasting followed by bingeing won't work in the short or long term.
Stay healthy with intermittent fasting
For both the 5:2 diet and 16:8 diet or any other type of intermittent fasting, it’s important that you choose what you eat carefully so that you’re still getting a well-balanced diet with all the vitamins and minerals required for health.
Consume lean protein found in meat, poultry and seafood, eggs, legumes like beans and lentils, nuts and seeds, as well as vegetables, fruit, and fibre. Meanwhile, cut down on sugar, refined grains, such as white rice, white bread and white flour, and processed foods.
Binge-eating is out: don’t break fasts with giant meals. You should also avoid snacking during the non-fasting period to get the benefits of the diet.
You need to stay hydrated while you’re in a fasting period, and should drink water at these times. Be aware that you may require more water than you think. Food actually provides a sizeable proportion of our daily water requirements, and therefore you might need to boost your intake in the fasting periods to avoid feeling thirsty or experiencing headaches.
Who is intermittent fasting suitable for?
Intermittent fasting is a diet many can try, but it isn’t right for diabetics, pregnant women and those who are breastfeeding, and children and adolescents. Those with anorexia or bulimia should also avoid this regime. It could also be that you’re on medication that has to be taken with food, and in this case, the diet won’t work for you. If you have a long term medical condition or are unsure, ALWAYS talk to your GP first.
Can intermittent fasting be done with other diets
The key to success with intermittent fasting is healthy eating, as we've said above. So if, for example, you want to try the keto diet, you can do it on an intermittent fasting schedule. Our advice? Make it easier on yourself and make one drastic change to your diet at a time and you're less likely to fail.