Is intermittent fasting worth trying? Benefits, limits and how to ease in

Many diets are hard to keep up. Low-calorie diets can leave you hungry and irritable. Low-carb and keto diets can bring headaches and cravings. Low-fat diets are hard to follow. Intermittent fasting focuses on when you eat rather than what, and comes in two main forms. With time-restricted eating, you eat within a window of about eight hours, such as 9 a.m. to 5 p.m. With whole-day fasting, you limit yourself to 400–600 calories on two or more days a week, as in the 5:2 diet, or on every other day.

Short-term trials show modest weight loss and lower risk factors for heart disease, including blood pressure, blood fats and inflammation. People seem to stick with intermittent fasting as well as, or better than, other diets. Most trials, though, last a year or less, so the long-term picture isn't clear yet. Fixed eating times may help you eat less, notice your habits and feel less deprived than you would counting calories. After about 12 hours without food, the body may begin burning stored fat, and a late-night snack interrupts that. A 2023 study also found that women who ate their last meal after 9 p.m. had a higher risk of heart disease and stroke.

If you want to try it, ease in gradually and fill your eating window with whole grains, nuts, beans, fruit and vegetables rather than fast food. Expect slow progress, around 0.25–0.5 kg (half a pound to a pound) a week, which is more likely to last. Talk to your doctor first, especially if you have diabetes or take medicine for blood pressure or heart disease, because longer fasts can upset your levels of sodium, potassium and other minerals.

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.