Fasting Shows No Weight-Loss Benefit Over Standard Meals in Randomized Trial

By Amy Orciari Herman

Edited by David G. Fairchild, MD, MPH, and Jaye Elizabeth Hefner, MD

Fasting for two thirds of the day does not lead to greater weight loss than eating meals throughout the day, according to a randomized trial in JAMA Internal Medicine.

Roughly 100 overweight or obese adults were assigned to time-restricted eating or consistent meal timing. In the time-restricted group, participants were advised to eat as needed from 12 p.m. until 8 p.m., and then fast for 16 hours until 12 p.m. the next day. In the consistent-meals group, participants were told to eat three structured meals across the day, with snacks as needed. There were no recommendations about caloric intake or physical activity.

At 12 weeks, mean weight loss did not differ significantly between the groups (0.94 kg with time-restricted eating and 0.68 kg with consistent meals). Most secondary outcomes, including changes in fat mass, lipids, and fasting glucose, also did not differ significantly between the groups. Of note, the time-restricted group lost more appendicular lean mass than the consistent-meals group.

The researchers conclude that the findings "do not support the efficacy of [time-restricted eating] for weight loss."