Maintaining a healthy weight isn’t just about food choices, it’s also about meal timing. Research published in International Journal of Behavioral Nutrition and Physical Activity found that two habits, increasing overnight fasting and eating breakfast earlier, were associated with lower body mass index (BMI) over time. The study was led by the Barcelona Institute for Global Health (ISGlobal), a center supported by the La Caixa Foundation.
The findings are based on data from more than 7,000 adults ages 40 to 65 who are members of GCAT | The Genomes for Life cohort is led by the German Institute Trias i Puyol (IGTP). In 2018, we asked participants to fill out detailed questionnaires regarding their height, weight, meal timing, lifestyle habits, and socio-economic background.
Five years later, in 2023, more than 3,000 of these people returned for follow-up. By recording updated measurements and collecting new survey data, researchers can now track changes over time and identify patterns.
Eating quickly and fasting for long periods of time lead to lower BMI
“In line with other recent research findings, our results suggest that extended overnight fasting, when accompanied by an early dinner and early breakfast, may help maintain a healthy weight. This is because eating earlier in the day aligns with your circadian rhythm and increases calorie burn and food intake. This may be because it improves desire regulation and helps maintain a healthy weight. However, it is too early to draw final conclusions and recommendations must await more solid evidence, ”explains ISGlobal researcher Luciana Pons Muzzo. At the time of his study abroad, he was currently studying at IESE Business School.
Gender differences and lifestyle patterns
When researchers compared the results by gender, they found significant differences. Women generally had a lower BMI, followed a Mediterranean diet, and were less likely to drink alcohol. At the same time, they reported poor mental health and were often responsible for home and family supervision.
Using a method called “cluster analysis,” the team grouped participants with similar characteristics. One small group of men stood out. These people usually ate their first meal after 14:00 and fasted for about 17 hours. They were more likely to smoke and drink alcohol, be less physically active, and less likely to follow a Mediterranean diet than their peers. They also tended to have lower levels of education and higher unemployment rates. The researchers did not observe a similar pattern among women.
intermittent fasting and skipping breakfast
“There are a variety of ways to practice so-called ‘intermittent fasting,’ and our study concerns one of them, overnight fasting. What we observed in a subgroup of men who practice intermittent fasting, which involves skipping breakfast, suggests that this practice has no effect on body weight. “Other intervention studies with obese participants have shown that this tactic is no more effective than reducing calorie intake in long-term weight loss,” says ISGlobal researcher and senior Camille LaSalle. Co-author of the study.
Chrononutrition and body clock
“Our study is part of an emerging field of research known as ‘chrononutrition,’ which focuses on analyzing not only what we eat, but also the time of the day and the number of meals we eat,” says Anna Palomar-Cros, a researcher at ISGlobal at the time of the study and now at IDIAP Jordi Gol. “Underlying this research is the knowledge that abnormal food intake patterns can conflict with the circadian system, the set of internal body clocks that regulate day-night cycles and associated physiological processes,” she added.
Eating earlier is associated with a wide range of health benefits
This study builds on ISGlobal’s earlier research on chronotrophy. Previous research has shown that eating dinner and breakfast earlier in the day reduces the risk of cardiovascular disease and type 2 diabetes, supporting the idea that meal timing plays an important role in long-term health.
