When it comes to managing weight, the timing of meals may matter more than what people eat, according to a new study. Maintaining a longer overnight fast and eating breakfast earlier were associated with lower body mass index (BMI).
According to science news outlet ScienceDaily, researchers at the Barcelona Institute for Global Health (ISGlobal) in Spain analyzed the relationship between meal timing and health indicators in more than 7,000 adults aged 40 to 65. The findings were published in the latest issue of the International Journal of Behavioral Nutrition and Physical Activity.
In 2018, the researchers surveyed participants' height, weight, meal times, lifestyle habits and socioeconomic conditions. Five years later, they conducted a follow-up survey with more than 3,000 people from the same group to compare changes.
The results showed that participants who maintained longer overnight fasting periods and had their first meal of the day earlier tended to have relatively lower BMI. The researchers interpreted this pattern as aligning with the body's circadian rhythm, which could improve energy expenditure efficiency and positively affect appetite regulation.
"When overnight fasting and early eating habits work together, they may help with weight management," said Luciana Pons-Muzzo, who led the study. "Eating earlier in the day may be advantageous in terms of metabolism and appetite regulation." She added, however, that "for now, the findings are at the level of correlation, and further verification is needed."
Differences by gender also emerged. Women generally had lower BMI than men, were more likely to follow a Mediterranean diet and drank less alcohol. On the other hand, they reported more negative mental health status and carried a heavier burden of housework and caregiving.
In subgroup analysis, the meal patterns of some male groups stood out. They tended to have their first meal late in the afternoon and maintain long fasting periods. However, this group showed higher rates of smoking and drinking, lacked physical activity and had relatively lower diet quality. Their education levels and employment status were also more vulnerable compared with other groups. This pattern was not observed among women.
Intermittent fasting involving skipping breakfast did not show a clear link with weight loss. Co-researcher Camille Lassale said, "The effect of intermittent fasting, including skipping breakfast, on weight was limited," adding that "many previous studies have also failed to demonstrate meaningful long-term weight loss effects."
The researchers said the findings connect with a research trend known as "chrononutrition," an approach that considers not only the content of meals but also when and how often they are consumed. "When irregular meal times clash with the body clock, they can affect metabolic processes," said Anna Palomar-Cros. "The role of meal timing in health needs to be continuously verified."
The study builds on prior research exploring the connection between meal timing and chronic diseases. Earlier research has reported that eating earlier in the day is associated with a reduced risk of cardiovascular disease and type 2 diabetes. The researchers suggested that adjusting meal timing could be used as a strategy for managing not only weight but also overall health.
