The Fast Diet: how to do it

Intermittent fasting is flexible and manageable. Go with a timetable that suits you, says The Fast Diet co-author Mimi Spencer

The reason for Intermittent Fasting – briefly but severely restricting the amount of calories you consume – is that by doing so you are hoping to “fool” your body into thinking it is in a potential famine situation and that it needs to switch from go-go mode to maintenance mode.


The reason our bodies respond to fasting in this way is that we evolved at a time when feast and famine were the norm. Our bodies are designed to respond to stresses and shocks; it makes them healthier, tougher. The scientific term is hormesis – that which does not kill you makes you stronger.

The benefits of fasting include:

– Weight loss
– A reduction of IGF-1, which means that you are reducing your risk of a number of age-related diseases, such as cancer
– The switching-on of countless repair genes in response to this stressor
– Giving your pancreas a rest, which will boost the effectiveness of the insulin it produces in response to elevated blood glucose. Increased insulin sensitivity will reduce your risk of obesity, diabetes, heart disease and cognitive decline
– An overall enhancement in your mood and sense of wellbeing. This may be a consequence of your brain producing increased levels of neurotrophic factor, which will hopefully make you more cheerful, which in turn should make fasting more doable.

When to eat

Michael tried several different fasting regimes. The one he settled on as the most realistic and sustainable was a fast on two non-consecutive days each week, allowing 600 calories a day, split between breakfast and dinner. This pattern has been called, for obvious reasons, a 5:2 diet – five days off, two days on, which means that the majority of your time is spent gloriously free from calorie-counting. On a fast day, he’ll normally have breakfast with his family around 7.30am and then aim to have dinner with them at 7.30pm, with nothing eaten in between. That way, he gets two 12-hour fasts in a day, and a happy family at the end of it.

The seven fasting sample menu suggestions printed here are based on his experience, providing the most straightforward and convincing Intermittent Fasting method.

I found that a slightly different pattern works for me. Sticking to the Fast Diet’s central tenet, on my fast days I eat 500 calories – but as two meals with a few snacks (an apple, some carrot sticks) in between, simply because the vast plain between breakfast and supper feels too great, too empty for comfort.

Some people who don’t feel hungry at breakfast would rather eat later in the day. That’s fine, go with a timetable that suits you. Some fasters will appreciate the convenience and simplicity of a single 500- or 600-calorie meal, allowing them to ignore food entirely for most of the day. Whatever you choose, it must be your plan.

What to drink

Plenty – as long as it doesn’t have a substantial calorie content. Drink plenty of water – it’s calorie-free, actually free, filling and will stop you confusing thirst for hunger.

On fast days we drink our tea and coffee black and sugarless; if you prefer it with milk and artificial sweeteners, fine. But beware that the calories in milk add up, and what you are trying to do is extend the time you are not consuming any calories at all.

Just hold out until tomorrow

Perhaps the most reassuring, and game-changing, part of the Fast Diet is that it doesn’t last for ever. Unlike deprivation diets that have failed you before, on this plan, tomorrow will always be different. There may be pancakes for breakfast, or lunch with friends, wine with supper, apple pie with cream. This On/Off switch is critical. It means that, on a fast day, though you’re eating a quarter of your usual calorie intake, tomorrow you can eat as you please. There’s boundless psychological comfort in the fact that your fasting will only ever be a short stay, a brief break from food. When you’re not fasting, ignore fasting – it doesn’t own you, it doesn’t define you. You’re not even doing it most of the time. Unlike full-time fad diets, you’ll still get pleasure from food, you’ll still have treats, you’ll engage in the regular, routine, food-related events of your normal life. There are no special shakes, bars, rules, points, affectations or idiosyncrasies. No saying “no” all the time. For this reason, you won’t feel serially deprived – which, as anyone who has embarked on the grinding chore of long-term, every-day dieting, the kind that makes you want to commit hara-kiri right there on the kitchen floor every time you open the fridge door, is precisely why conventional diet plans fail.

Who should avoid fasting?

There are certain groups for whom fasting is not advised. Type 1 diabetics are included in this list, along with anyone suffering from an eating disorder. If you are already extremely lean, do not fast. If you are pregnant or trying to get pregnant you should not fast. Children should never fast; they are still growing and should not be subject to nutritional stress of any type. If you have an underlying medical condition, visit your GP, as you would before embarking on any weight-loss regime.

Find out more about the benefits of The Fast Diet, and the science behind it.

See seven fasting day menu examples.


Buy your copy of the Fast Diet now.