Fasting intermittently is incredibly effective when it comes to losing weight, and in fact giving your digestive system a break may do wonders for your health.
Since the success of the 5:2 diet, in which you eat normally for five days, then restrict calories to 500-800 daily for two days, the thinking on weight loss has shifted.
“The reality is you’ve got a lot of clinically obese people who are metabolically healthy and a proportion of lean people who are metabolically unhealthy,” says Adam Collins, principal teaching fellow in nutrition at the University of Surrey.
Metabolic ill-health is linked to cardiovascular disease, diabetes and all-round sluggishness, which deters physical activity, which intensifies the problem. “You can almost always root down to the fact that we’re replete and always have a layer of food for our guts to deal with. So your appetite suppression signals stop working,” Collins says. As the nutritionist Alice Mackintosh once told me, “There is basic housekeeping your gut has to do, which it can’t do when it’s full.”
Probably the simplest change to make, Collins explains, is to lengthen your overnight fast, which is a fancy way of saying skip breakfast. “Even intermittent breakfast-skipping could have an impact,” he says. You don’t need to restrict your calories after that; just avoid bingeing. If you want to get experimental with the rest of your diet, you could try “carb cycling”, alternating between high- and low-carb periods.
This is not a recent discovery. There are studies which go back decades, which found that energy-restricted mice live longer.