A recent study suggests that there are patterns in the relationship between meal times and body weight, with the scientists saying that to keep weight in check, it’s not only important to consider what we eat, but also the times at which we do so.
They said two specific habits are associated with a lower body mass index (BMI) in the long term: keeping a longer overnight fast and eating breakfast early.
The study, published in the International Journal of Behavioral Nutrition and Physical Activity, was led by the Barcelona Institute for Global Health (ISGlobal), a centre supported by the “la Caixa” Foundation.
The research involved more than 7 000 volunteers aged 40-65 from the GCAT | Genomes for Life cohort, a project led by the Germans Trias i Pujol Research Institute (IGTP).
In 2018, participants completed questionnaires about their weight and height, eating habits including meal times, other lifestyle habits and socio-economic status. Five years later, in 2023, more than 3 000 of them made a follow-up visit to the research team, where their measures were registered again and new questionnaires completed.
Interpretation of results
“Our results, in line with other recent studies, suggest that extending the overnight fast could help maintain a healthy weight if accompanied by an early dinner and an early breakfast,” said Luciana Pons-Muzzo, researcher at ISGlobal at the time of the study and currently at IESE Business School.
“We think this may be because 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 soon to draw definitive conclusions, so recommendations will have to wait for more robust evidence.”
Gender differences
Analysis of the data by gender showed that compared with men, women generally had lower BMI, higher adherence to the Mediterranean diet, lower propensity to consume alcohol, poorer mental health, and were more likely to be responsible for household or family supervision.
The team used a statistical technique called “cluster analysis” to group 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 was after 2pm and who, on average, fasted for 17 hours.
Compared with the rest, this group of men tended to have less healthy lifestyles (more likely to smoke, drink alcohol, less physical activity, less adherence to the Mediterranean diet), lower levels of education, and were more likely to be unemployed.
These patterns were not observed in any group of women.
On intermittent fasting
“There are different ways of practising what is known as ‘intermittent fasting’ and our study relates to one of them, which is overnight fasting. What we observed in a subgroup of men who do intermittent fasting by skipping breakfast is that this has no effect on body weight.
“Other intervention studies in participants with obesity have shown this tactic is no more effective than reducing calorie intake in reducing body weight in the long term,” said Camille Lassale, ISGlobal researcher and senior co-author of the study.
The team said their research was part of an emerging field of research known as “chrono-nutrition”, which focuses not only on analysing what people eat, but also the times of day and the number of times they eat.
“At the basis of this research is the knowledge that unusual food intake patterns can conflict with the circadian system, the set of internal clocks that regulate the cycles of night and day and the physiological processes that must accompany them,” said Anna Palomar-Cros, researcher at ISGlobal at the time of the study and currently at IDIAP Jordi Gol.
Previous studies
This study provides continuity to a line of ISGlobal research on chrono-nutrition, which in recent years has published two other studies with results in the same direction. In these studies, it was observed that eating dinner and breakfast early was associated, respectively, with a lower risk of cardiovascular disease and type 2 diabetes.
Study details
Sex-specific chrono-nutritional patterns and association with body weight in a general population in Spain (GCAT study)
Luciana Pons-Muzzo, Rafael de Cid, Mireia Obón-Santacana, Kurt Straif, Kyriaki Papantoniou, Isabel Santonja, Manolis Kogevinas, Anna Palomar-Cros, Camille Lassale.
Published in the International Journal of Behavioural Nutrition and Physical Activity on 12 September 2024
Abstract
Background
Altered meal timing patterns can disrupt the circadian system and affect metabolism. Our aim was to describe sex-specific chrono-nutritional patterns, assess their association with body mass index (BMI) and investigate the role of sleep in this relationship.
Methods
We used the 2018 questionnaire data from the population-based Genomes for Life (GCAT) (n = 7074) cohort of adults aged 40–65 in Catalonia, Spain, for cross-sectional analysis and its follow-up questionnaire data in 2023 (n = 3128) for longitudinal analysis. We conducted multivariate linear regressions to explore the association between mutually adjusted meal-timing variables (time of first meal, number of eating occasions, nighttime fasting duration) and BMI, accounting for sleep duration and quality, and additional relevant confounders including adherence to a Mediterranean diet. Finally, cluster analysis was performed to identify chrono-nutritional patterns, separately for men and women, and sociodemographic and lifestyle characteristics were compared across clusters and analysed for associations with BMI.
Results
In the cross-sectional analysis, a later time of first meal (β 1 h increase = 0.32, 95% CI 0.18, 0.47) and more eating occasions (only in women, β 1 more eating occasion = 0.25, 95% CI 0.00, 0.51) were associated with a higher BMI, while longer nighttime fasting duration with a lower BMI (β 1 h increase=-0.27, 95% CI -0.41, -0.13). These associations were particularly evident in premenopausal women. Longitudinal analyses corroborated the associations with time of first meal and nighttime fasting duration, particularly in men. Finally, we obtained 3 sex-specific clusters, that mostly differed in number of eating occasions and time of first meal. Clusters defined by a late first meal displayed lower education and higher unemployment in men, as well as higher BMI for both sexes. A clear “breakfast skipping” pattern was identified only in the smallest cluster in men.
Conclusions
In a population-based cohort of adults in Catalonia, we found that a later time of first meal was associated with higher BMI, while longer night-time fasting duration associated with a lower BMI, both in cross-sectional and longitudinal analyses.
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