Brain Power

a healthy brain is about feeling good

One good example is that vitamin C helps with the absorption of iron.

Blueberries to boost your memory. Eggs to stop your brain shrinking. Sage to help you concentrate.

Thuret once told me she follows a fasting pattern in which she eats every other day (on fasting days she still eats, opting for something like a latte, fruit and a cereal bar).

However, some of the habits that fasting brings – like making us more aware of what we are eating, and not snacking late into the evening – can be beneficial more generally, not least because our digestive system has its own circadian rhythm and works better earlier on in the day. Besides, waiting a few hours might just make your breakfast taste even more delicious.

You’ve probably heard of many of these: the 5:2 diet involves eating normally for five days a week and severely restricting calorie intake the other two; the 8:16 diet has you eating during an eight-hour window; the OMAD diet (or one meal a day) restricts food to just one hour; and alternate-day fasting is self-explanatory.

This cycle of fast and famine may even have contributed to the complexity of the human brain, with the pressure of food scarcity forcing its evolution, says Mark Mattson who studies fasting at Johns Hopkins University.

All this has led to an explosion in the popularity of a plethora of fasting diets, which each involve a period of time with no, or very little food intake, followed by normal eating.

This process, called ketosis, is thought to underpin many of the possible beneficial effects associated with fasting, and is the concept behind the popular ketogenic diet, where people eat next to no sugars and other carbohydrates, so the body burns fat stores instead.

Ketones have been shown in animal studies to trigger numerous health-promoting processes, including the production of BDNF (a molecule that plays an important part in learning and memory) – which might explain the anecdotal reports that people feel mentally sharper when they fast – and trials are underway to see whether the same thing happens in humans too.