It seemed like a magic solution when the idea was first popularised by Dr Michael Mosley: “fast” for two days in the week, consuming between 500 calories (women) and 600 calories (men), and then eat a healthy, balanced diet for the remaining five days.
Since then, the term intermittent fasting has been used to describe any window where you don’t eat; typically, eight hours.
“The idea is that fasting creates a calorie deficit, which means that once the body uses up its carbohydrates stored in the liver and muscles, it relies on fat stores for energy instead, which can lead to weight loss,” says Sarah Coe, nutrition scientist at the British Nutrition Foundation.
“There is some evidence from clinical trials to suggest that intermittent fasting can help with weight loss. But the evidence for the 5:2 diet specifically is limited compared to other weight-loss diets.”
Importantly, evidence from clinical trials also suggests that forms of intermittent fasting such as the 5:2 diet don’t appear to be any more effective than more traditional weight-loss diets with continual daily calorie restriction.
“There is also some evidence to suggest that intermittent fasting could bring other health benefits, including improved blood pressure and blood-glucose control, and lower cholesterol levels, which could reduce the risk of disease. But compared to other types of weight-loss diets, the amount of evidence for any specific health benefits of intermittent fasting is limited,” says Coe.
Many of the studies are short term or in small numbers of subjects, or have been done in animals, so more research is needed to explore the possible long-term health benefits in humans.
The 5:2 diet can be restrictive, and some people may find it challenging to stick to in the long term, particularly as it can result in hunger and low energy levels, disrupting work or social plans.
For the 5:2 diet to work, it’s important to stick to the calorie limits on “fast” days and not go overboard on the “normal” days, as this can hinder any weight loss or could even lead to weight gain.
The 5:2 diet isn’t recommended…