Diet Review: Intermittent Fasting for Weight Loss
by The Nutrition Source · Harvard T.H. Chan School of Public Health
Harvard Nutrition Source review of alternate-day fasting, 5:2 and time-restricted eating. Summarizes trial results showing modest weight loss no better than daily calorie restriction, plus who should avoid fasting and the gaps in long-term evidence.
More resources on Metabolic Health & Fasting
Obesity Energetics: Body Weight Regulation and the Effects of Diet Composition
NIH review of how the body regulates weight and resists weight loss. It includes a meta-analysis of 32 controlled feeding studies that found no meaningful fat-loss advantage for low-carb over low-fat diets when calories were equal, testing the carbohydrate-insulin model.
Intermittent fasting strategies and their effects on body weight and other cardiometabolic risk factors: systematic review and network meta-analysis
The most current, highest level of human evidence on whether fasting beats ordinary calorie restriction for metabolic markers. BMJ 2025 network meta-analysis of randomised trials comparing time-restricted eating, alternate-day fasting and whole-day fasting with continuous calorie restriction on weight, glucose, insulin and lipids. It finds broadly similar effects, with only small differences between them.
Effects of Intermittent Fasting on Health, Aging, and Disease
NEJM review of the physiology of intermittent fasting: the metabolic switch from glucose to ketones, cellular stress-response pathways, and animal and human findings on obesity, diabetes, heart disease and aging. Much of the evidence is from animals. No free resource of equal authority explains the mechanisms (metabolic switching, adaptive stress responses) that underlie most popular fasting claims.