In a randomised trial, time-restricted eating did not enhance the effect of calorie restriction on weight loss.

Time-restricted eating (i.e. confining calorie intake to a limited period of each day) leads to weight loss in animals, possibly because calories are consumed only during metabolically active periods. Human studies have shown weight loss benefits with time-restricted eating (e.g. NEJM JW Gen Med Oct 1 2022 and JAMA Intern Med 2022; 182: 953-962) but have not consistently controlled for total calorie intake.

Investigators addressed this issue with a randomised, controlled trial in which 41 adults (mean age, 59 years) with obesity (mean weight, 99 kg) and prediabetes or diet-controlled diabetes received isocaloric diets with equivalent micro- and macronutrient composition; calorie amounts were based on metabolic needs and activity levels. Food was prepared in a study kitchen and consumed onsite or taken home. The intervention group was instructed to eat between 8 a.m. and 6 p.m. and to consume 80% of calories by 1 p.m. The control group was instructed to eat between 8 a.m. and midnight, with 55% of calories after 5 p.m.

Weight loss in the two groups was similar at 12 weeks (about 2.4 kg). Various glycaemic measures also did not differ between groups.

Comment: These results suggest that the benefits previously ascribed to time-restricted eating are simply due to calorie restriction, rather than timing of intake. The weight loss, which was modest but typical for a 12-week diet intervention, appears to be determined mostly by controlled calorie intake based on individual basal requirements.

Thomas L. Schwenk, MD, Professor Emeritus, Family and Community Medicine, University of Nevada School of Medicine, Reno, USA.

Maruthur NM, et al. Effect of isocaloric, time-restricted eating on body weight in adults with obesity: a randomized controlled trial. Ann Intern Med 2024; 177: 549-558.

This summary is taken from the following Journal Watch titles: General Medicine, Ambulatory Medicine.