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A new study led by the Barcelona Institute for Global Health (ISGlobal) suggests that adopting specific eating habits, such as extending the overnight fast and eating breakfast early, may help maintain a lower body mass index (BMI) in the long term. Published in the International Journal of Behavioral Nutrition and Physical Activity, the research involved over 7,000 participants and highlights the importance of not just what we eat but when we eat.
The study, part of the GCAT | Genomes for Life cohort project led by the Germans Trias i Pujol Research Institute (IGTP), followed participants aged 40 to 65 over five years. Initially, in 2018, volunteers answered detailed questionnaires about their eating habits, meal timing, lifestyle factors, and socioeconomic status. In 2023, more than 3,000 of them participated in follow-up assessments.
The findings indicate that keeping a longer overnight fast and eating breakfast earlier aligns with our circadian rhythms, potentially aiding in calorie burning and appetite regulation. “Our results suggest that extending the overnight fast, paired with an early dinner and breakfast, could help maintain a healthy weight,” said Luciana Pons-Muzzo, ISGlobal researcher at the time of the study.
Gender-Specific Findings
Interestingly, the analysis revealed significant gender differences. Women generally reported lower BMI, better adherence to the Mediterranean diet, less alcohol consumption, and poorer mental health compared to men. They were also more likely to be responsible for household supervision.
A unique pattern emerged among a small group of men who ate their first meal after 2:00 PM, fasting for 17 hours. This group tended to have less healthy lifestyles, including smoking, alcohol consumption, and lower levels of physical activity. The same trend was not observed in women, suggesting a possible gender-based difference in how meal timing affects BMI.
Intermittent Fasting Insights
The study also explored the effects of intermittent fasting, specifically overnight fasting. Contrary to popular belief, skipping breakfast did not appear to help with weight loss among a subgroup of men who practiced this form of fasting. “Intermittent fasting by skipping breakfast seems to have no significant effect on body weight,” explained Camille Lassale, ISGlobal researcher and co-author of the study. This is consistent with other studies showing that reducing calorie intake may be more effective for long-term weight loss than simply adjusting meal timing.
The Role of Chrononutrition
This research contributes to the growing field of chrononutrition, which examines not only the types of food consumed but also the timing of meals in relation to our internal circadian clocks. Disrupting these natural rhythms can lead to negative health outcomes. In earlier ISGlobal studies, eating meals earlier was associated with a lower risk of cardiovascular disease and type 2 diabetes, further underscoring the health benefits of aligned meal timing.
With growing evidence from chrononutrition studies, early breakfast and extending overnight fasting could play a crucial role in maintaining not only a healthy BMI but also overall well-being.
Reference:
Pons-Muzzo L, et al. Sex-specific chrono-nutritional patterns and association with body weight in a general population in Spain (GCAT study). International Journal of Behavioral Nutrition and Physical Activity (2024). DOI: 10.1186/s12966-024-01639-x.
