Does intermittent fasting help you lose weight? What a year-long trial found

Intermittent fasting for weight loss means shortening the hours you eat, rather than counting calories or cutting out foods. Writing for Harvard Health, Dr Richard Joseph notes that the body moves into an early fasted state about five to six hours after your last meal. The research, though, is hard to read: many studies are small and short, have no control group, and test different fasting schedules.

One of the clearest answers so far comes from a year-long trial published in the New England Journal of Medicine. The participants were adults aged 18 to 75 with obesity, and all of them cut their calories by about 25%. One group ate within an eight-hour window; the other ate the same amount at any time of day. Of the participants, 118 finished the year. The time-restricted group lost about 8 kg (18 lb) and the calorie-only group about 6 kg (14 lb), but the difference wasn't statistically significant. Blood pressure, cholesterol and blood sugar improved by similar amounts in both groups. Limiting the eating window, on its own, didn't add much.

Dr Joseph concludes that time-restricted eating is safe for most people and may lead to modest weight loss, around 3–8% of body weight, mainly because people end up eating fewer calories. Overeating in your eating window cancels that out, so what and how much you eat still matter. Some of the weight lost can be muscle, which is why he strongly recommends strength training alongside fasting. Take extra care if you have diabetes or an eating disorder, are pregnant or breastfeeding, or take medicine that has to be taken with food.

General information, not medical advice. Don’t fast without talking to a doctor if you’re pregnant or breastfeeding, under 18, have had an eating disorder, have diabetes, or take insulin or other medicine that lowers blood sugar.