Eating earlier in the day may offset genetic risk of obesity, study finds

Eating meals earlier in the day may help counteract genetic predisposition to obesity, according to new research led by scientists at the Complutense University of Madrid.

The study, published in the journal Obesity, found that meal timing plays a significant role in weight regulation, particularly among individuals with a high genetic risk for obesity. Researchers observed that those who ate earlier experienced less weight gain over time, despite genetic profiles that would typically predict greater weight increases.

Meal timing has garnered growing interest for its impact on metabolism, energy expenditure and alignment with the body’s circadian rhythms. So-called ‘zeitgebers’, biological cues that regulate the body’s internal clock, can synchronise metabolic tissues such as the liver, pancreas and fat stores. Altering food intake timing can shift these cues, potentially disrupting metabolic rhythms.

The body contains both a central circadian clock, which responds to environmental light and peripheral clocks in metabolic organs that are particularly sensitive to food intake. If these become misaligned, the resulting internal circadian disruption is thought to contribute to poor cardiometabolic health and increased obesity risk.

In the ONTIME study (Obesity, Nutrigenetics, Timing, and Mediterranean), researchers followed 1,195 adults living with overweight or obesity (average age 41 years, 80.8 per cent female) who were enrolled at six weight-loss clinics across Spain. Participants underwent a 16-week behavioural weight-loss programme, followed by a long-term follow-up assessment approximately 12 years later.

The team calculated a polygenic risk score for body mass index (BMI) using over 900,000 genetic markers and analysed the timing of daily meals. Meal timing was defined as the midpoint between a participant’s first and last meals of the day, adjusted for weekday and weekend variations.

Results showed that each additional hour of later meal timing was associated with a 0.952 kg/m² increase in baseline BMI and a 2.2 per cent rise in body weight over the 12-year follow-up period. Among individuals in the highest genetic risk group, BMI increased by 2.21 kg/m² for every hour of delayed eating. No such association was found among participants with lower genetic risk.

The authors concluded that earlier eating patterns are linked to better long-term weight maintenance and may help mitigate the impact of genetic risk. The findings suggest that meal timing could be a valuable component in personalised strategies to prevent and manage obesity.