A newly published study builds on growing evidence that the time of day someone eats has significant impacts on metabolic health – which directly affects a person’s risk of chronic diseases – with earlier eating associated with the clearest benefits. 

In a review published in the journal BMJ Medicine, researchers examined whether time-restricted eating (TRE) – dietary inventions where eating is confined to a restricted number of hours in the day – can improve metabolic outcomes and explored whether particular TRE patterns are more effective than others.

The systematic review looked at the results of 41 randomised controlled trials, in which of 2287 participants were included. TRE was categorised according to time of eating and specific duration, or window, of eating each day (less than 8 hours, eight  hours, and greater than 8  hours). Early-time-restricted eating meant the last meal was eaten before 5pm, while mid-time was a meal ending between 5-7pm and late-time was ending a meal after 7pm.

Regardless of eating ‘time window’, TRE was linked with improvements in a broad range of metabolic outcomes compared with usual diets. These include improved body weight, body mass index, fat mass, waist circumference, systolic blood pressure, and levels of fasting blood glucose, fasting insulin, and triglycerides. 

But the clearest benefits were seen with early TRE over late eating, which was consistently associated with greater reductions in body weight, waist circumference, and fasting insulin levels than late TRE. 

The researchers concluded that early time restricted eating was superior to late time restricted eating, and that prioritizing earlier eating windows may offer promise as a simple, low-cost approach to improving population metabolic health. 

The effects of the duration of TRE eating periods (short, medium or long) were generally found to be inconsistent.