Keeping a longer overnight fast and eating an early breakfast may be associated with a lower body mass index.

The study involved more than 7,000 volunteers aged 40 to 65 from GCAT | Genomes for Life cohort, a project led by the German Research Institute Trias i Pujol (IGTP). In 2018, participants completed questionnaires about their weight and height, eating habits including meal times, other lifestyle habits, and socioeconomic status. In 2023, after five years, more than 3,000 participants made a follow-up visit to the research team, where their measurements were recorded again and new questionnaires were completed.

Interpretation of results

“Our results, in line with other recent studies, suggest that extending overnight fasting could help maintain a healthy weight if accompanied by an early dinner and breakfast. We believe this may be due to the fact that eating earlier in the day is more in line with circadian rhythms and allows for better calorie burning and appetite regulation, which can help maintain a healthy weight However, it is too early to shoot. definitive conclusions, so recommendations will have to wait for more solid evidence”, explains Luciana Pons-Muzzo, researcher. at ISGlobal at the time of the study and currently at IESE Business School.

Gender differences

Analysis of data by gender showed that, compared to men, women generally had a lower BMI, greater adherence to the Mediterranean diet, a lower propensity to consume alcohol, poorer mental health and were more likely to be responsible for monitoring the household or family.

The team used a statistical technique called ‘cluster analysis‘ group together individuals with similar characteristics. From the results of this analysis, the authors were struck by a small group of men whose first meal of the day took place after 2 p.m. and who, on average, fasted for 17 hours. Compared to the rest, this group of men tended to have a less healthy lifestyle (more likely to smoke, drink alcohol, less physical activity, less adherence to the Mediterranean diet), had a lower level of lower education and was more likely to be unemployed. . These trends were not observed in any group of women.

On intermittent fasting

“There are different ways to practice what is called ‘intermittent fasting’ and our study focuses on one of them, which is night fasting. What we observed in a subgroup of men who practice intermittent fasting by skipping breakfast is that this practice has no effect on body weight. Other intervention studies in obese participants have shown that this tactic does not. more effective than reducing calorie intake for reducing body weight in the long term,” explains Camille Lassale, researcher at ISGlobal and co-lead author of the study.

“Our research is part of an emerging area of ​​research called ‘chrononutrition,’ which focuses not only on analyzing what we eat, but also what times of day and how many times we eat,” explains Anna Palomar-Cros, researcher at ISGlobal at the time of the study and currently at IDIAP Jordi Gol. “Underpinning this research is the knowledge that unusual eating patterns can conflict with the circadian system, the set of internal clocks that regulate night and day cycles and the physiological processes that must accompany them.” , she adds.

Previous studies

This study is a continuation of a line of research by ISGlobal on chrononutrition, which has published two other studies in recent years with results in the same direction. In these studies, it was observed that early dinner and early breakfast were associated with a lower risk of cardiovascular disease and type 2 diabetes, respectively.