Two habits stood out in a long-term study of adults in Spain. Eating breakfast early, and stretching the overnight fast between dinner and the next morning's first meal, were both independently linked to a lower body mass index (BMI) years later.
The analysis was carried out by researchers at the Barcelona Institute for Global Health (ISGlobal) and published in the International Journal of Behavioral Nutrition and Physical Activity. It drew on more than 7,000 adults aged 40 to 65 in the Catalan GCAT cohort, with roughly 3,000 followed up around five years later.
"Extending the overnight fast could help maintain a healthy weight if accompanied by an early dinner and an early breakfast," said Luciana Pons-Muzzo, a researcher at ISGlobal at the time of the study and now at IESE Business School.
Why the body prefers food early
The mechanism sits in the field of chrononutrition, the study of how meal timing interacts with the body's internal clock. Insulin sensitivity, the ease with which cells absorb sugar from the blood, is naturally higher in the morning and falls as the day goes on.
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That means the same slice of toast handled well at 8 a.m. can spike blood sugar higher at 10 p.m. A 2019 trial in healthy men reported that two weeks of eating earlier in the day improved whole-body insulin sensitivity and skeletal muscle glucose uptake, even without weight loss.
Eating earlier is "more in line with circadian rhythms and allows for better calorie burning and appetite regulation," Pons-Muzzo said.
The trap of skipping breakfast
Skipping breakfast to squeeze eating into a later window did not deliver the same benefit in the Spanish data. A subgroup of men who did not eat until after 2 p.m., fasting around 17 hours, showed no weight advantage.
"What we observed in a subgroup of men who do intermittent fasting by skipping breakfast is that this practice has no effect on body weight," said Camille Lassale, an ISGlobal researcher and senior co-author.
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That aligns with a wider pattern in the research: the metabolic upside of time-restricted eating appears strongest when the eating window sits earlier in the day, not later. Delaying the first meal pushes calories into the evening, when insulin sensitivity is lower and the body is preparing for rest.
What this looks like at the breakfast table
Nutrition experts writing about breakfast timing often point to a window within roughly two hours of waking, around 7 to 8 a.m. for most people. "If you don't have a really good breakfast, people often overcompensate at lunch and dinner," Gabrielle Gambino, a senior dietitian at NewYork-Presbyterian's Weill Cornell Medical Center, told The Digger News.
There is no single clock that fits everyone. Shift workers, people with diabetes and those on certain medications may need a different rhythm, and anyone with a medical condition should talk to their doctor before overhauling their meal schedule.
The practical takeaway from the ISGlobal work is narrower than any diet trend. Pulling breakfast forward, finishing dinner earlier, and letting the body rest between the two is a pattern the same schedule research keeps returning to, and one that appears to sit closer to how human metabolism was built to run. It also fits neatly with the growing evidence that when you eat can quietly move blood pressure over time, independent of what is on the plate.
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This article is made and published by Jesper Bengtson, who may have used AI in the preparation.