It’s long been thought late night snacking can lead to weight gain. Few studies, though, have investigated the effects of late eating on the three main players in body weight regulation: regulation of calorie intake, the number of calories you burn and molecular changes in fat tissue.
Now, a new study from Brigham and Women’s Hospital found that when we eat significantly impacts our energy expenditure, appetite and molecular pathways in adipose tissue.
Previous research conducted by the study team others have shown that late eating is associated with increased obesity risk, increased body fat and impaired weight loss success. The researchers wanted to understand why.
They asked, “does the time that we eat matter when everything else is kept consistent”? They found that eating four hours later makes a significant difference for our hunger level, the way we burn calories after we eat, and the way we store fat.
About the study
The in-laboratory experiment had 16 healthy adults with overweight or obesity complete two six-day diet protocols: an early eating protocol with meals at 8 am, noon and 4 pm and a late eating protocol with the exact same meals scheduled at noon, 4 pm and 8 pm.
In the last two to three weeks before starting each of the protocols, participants maintained fixed sleep and wake schedules, and in the final three days before entering the laboratory, they strictly followed identical diets and meal schedules at home.
In the lab, participants regularly documented their hunger and appetite, provided frequent small blood samples throughout the day and had their body temperature and energy expenditure measured.
To measure how eating time affected molecular pathways involved in how the body stores fat, investigators collected biopsies of adipose tissue from a subset of participants in both the early and late eating protocols.
Hunger increases, calorie-burning decreases with late eating
The results revealed that eating later had profound effects on hunger and appetite-regulating hormones called leptin and ghrelin, which influence our drive to eat. Levels of leptin, which signals satiety, were decreased across the 24 hours in the late eating group compared to the early eating group.
When participants ate later, they also burned calories at a slower rate. As well, among late eaters, gene activity in adipose tissue showed changes indicating increased fat storage and decreased fat burning.
These findings are consistent with a large body of research suggesting that eating later may increase the risk of obesity. They also shed new light on how this might occur.
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