Adapting Diet to Chronotype Boosts Weight Loss, Gut Health

Among patients with overweight/obesity, a diet adapted to an individual’s chronotype was more effective in promoting weight loss and improving cardiometabolic health and gut microbiota (GM) than a conventional low-calorie diet.

“Emerging evidence suggests that aligning dietary patterns with an individual’s circadian rhythm, or chronotype, may optimize metabolic processes and gut microbiota (GM) composition and function,” the study authors wrote. “Given the burden of obesity, a chronotype-adapted diet — aligning meal timing with biological rhythms — could be an innovative approach to weight management.”

The study, presented at NUTRITION 2025 in Orlando, Florida, showed that, overall, fat percentages decreased significantly in the intervention group, while the control group showed no significant change. In addition, a GM analysis revealed greater production of anti-inflammatory short-chain fatty acids (SCFAs) in the intervention group than in the control group.

For clinicians, considering a patient’s chronotype during dietary counseling would be “a practical and feasible starting point,” principal author Monica Dinu, PhD, assistant professor at the University of Florence, Florence, Italy, told Medscape Medical News. “This can be done easily with a simple [tool] like the Morningness-Eveningness Questionnaire (MEQ).”

Aligning Meals With Chronotype

Researchers conducted a 4-month, open-label, randomized controlled trial. A total of 140 adults with overweight/obesity were assigned to either a chronotype-adapted, low-calorie diet with meal timing tailored to their metabolic peaks (morning vs evening chronotype) or a standardized low-calorie eating plan. Chronotype was determined using the MEQ, which offers “a practical, noninvasive method that can be easily applied in both research and ambulatory settings,” Dinu noted.

The team did not impose strict time windows for meals, she said. “Rather, the intervention was based on the distribution of energy intake throughout the day. Morning chronotypes consumed approximately 80% of their daily energy intake in the earlier part of the day (including lunch), whereas evening chronotypes consumed the majority in the later part (also including lunch).”

“The dietary intervention adhered to the principles of the Mediterranean diet, and we did not recommend any fasting periods,” she added. “Our focus was on aligning meal timing with individual chronotype rather than restricting eating windows.”

Both diets had an equivalent daily calorie content, adjusted according to gender and starting weight. The primary outcome was weight change. Secondary outcomes were changes in body composition, biochemical markers, GM composition, and SCFAs.

Which Chronotype Worked Better?

A total of 117 participants (84%; mean age 49 years) completed the study (57 in the intervention group and 60 in the control group). While participants in both intervention groups experienced significant weight loss, reductions were greater in evening chronotypes (−3.7 kg) than in morning chronotypes (−3.2 kg) and control participants (−2.5 kg).

Fat mass percentages decreased significantly in the intervention groups (−2.8% in evening and −1.6% in morning chronotypes), whereas the control group showed no significant change (−0.5%). Both the intervention groups showed reductions in total and low-density lipoprotein cholesterol levels, but only morning chronotypes showed a significant decrease in glucose levels (−2.9 mg/dL).

A GM analysis revealed enrichment of SCFA-producing bacteria, such as Clostridiales vadin BB60, and a reduction in Nitrososphaeraceae in the intervention groups, accompanied by an increased production of anti-inflammatory SCFAs compared with the control group: Isobutyric acid, +0.42% vs −0.25%; 2-methylbutyric acid, +0.43% vs −0.44%).

The team concluded that a chronotype-adapted diet may be more effective than a standard low-calorie diet in improving body composition, metabolic risk profile, and GM in individuals with overweight/obesity — particularly among evening chronotypes.

“Evening chronotypes also experienced greater weight loss and reported reduced hunger despite consuming more calories later in the day, a timing typically discouraged,” Dinu noted.

“For individuals with an evening chronotype, adjusting the distribution of energy intake to better match their biological rhythms may lead to more effective and sustainable weight management,” she added. “While further research is needed, these findings support the potential of chronotype-based strategies as part of a personalized approach to dietary intervention.”

The research received no specific grant. No conflicts of interest were declared.

Marilynn Larkin, MA, is an award-winning medical writer and editor whose work has appeared in numerous publications, including Medscape Medical News and its sister publication MDedge, The Lancet (where she was a contributing editor), and Reuters Health.