Does the time of day you eat affect how quickly you age?

The timing of meals influences your metabolism, and there are indications that this also affects how you age. A large observational study of more than 24,000 Americans found that people who ate fewer than 3 meals per day, or who fasted for less than 10 hours or more than 14 hours overnight, had higher biological age scores in their blood. The sweet spot for overnight fasting therefore appears to be 10 to 14 hours, but this is observational: you cannot draw conclusions about cause and effect from it.

Eating early in the day appears to be beneficial. In a small randomised study of 11 adults, average blood sugar dropped noticeably after just 4 days when all meals fell between 08:00 and 14:00. The activity of genes involved in slowing ageing and cellular clean-up also increased. These are promising signals, but the study was too small and too short to draw firm conclusions from.

Eating at times that clash with your internal biological clock, such as regularly eating late in the evening or at night, is associated with higher health risks: more inflammation, a less healthy gut microbiome and worse metabolic markers. A prospective study of nearly 9,500 Koreans over 3.5 years showed that night-time snacking increased the risk of obesity by 20 to 26%. Obesity is itself a risk factor for accelerated ageing.

Intermittent fasting and a restricted daily eating window can, in animal studies, replicate many of the effects also seen with caloric restriction. Whether this also meaningfully slows ageing in humans has not yet been demonstrated. Moreover, the biological rhythm itself changes as we grow older, which makes it difficult to recommend a single approach for everyone.

It is not only about timing, by the way. How much protein you eat per meal also matters for healthy ageing: research points to an intake of at least 1.2 to 1.6 grams of protein per kilogram of body weight per day to help prevent muscle loss in later life. Timing and the distribution of protein throughout the day both play a role in this.