Eating late increases hunger, decreases calories burned

Boston - While popular healthy diet mantras advise against midnight snacking, few studies have comprehensively investigated the simultaneous effects of late eating.

A new study by Brigham and Women's Hospital in Boston, the US, has found late eating causes decreased energy expenditure, increased hunger and changes in fat tissue that combined may increase obesity risk.

Obesity afflicts approximately 42 percent of the developed world’s population and contributes to the onset of chronic diseases, including diabetes, cancer, and other conditions.

While popular healthy diet mantras advise against midnight snacking, few studies have comprehensively investigated the simultaneous effects of late eating on the three main players in body weight regulation and thus obesity risk.

They are regulation of calorie intake, the number of calories you burn, and molecular changes in fat tissue.

The Brigham and Women's Hospital research found that when people we eat significantly impacts our energy expenditure, appetite, and molecular pathways in adipose tissue. Their results are published in Cell Metabolism.

The researchers wanted to explain why late eating increases obesity risk. Previous studies had shown late eating is associated with increased obesity risk, increased body fat, and impaired weight loss success. The Brigham study wanted to know why.

The researchers found that eating four hours later makes a significant difference to hunger levels, the way people burn calories after they eat, and the way they store fat.

They studied patients with a body mass index (BMI) in the overweight or obese range. Each participant completed two laboratory protocols: one with a strictly scheduled early meal schedule, and the other with the exact same meals, each scheduled about four hours later in the day.

In the last two to three weeks before starting each of the in-laboratory 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.

Results revealed eating later had profound effects on hunger and appetite-regulating hormones leptin and ghrelin, which influence the drive to eat.

Specifically, levels of the hormone leptin, which signals satiety, were decreased across the 24 hours in the late eating condition compared to the early eating conditions. When participants ate later, they also burned calories at a slower rate and exhibited adipose tissue gene expression towards increased adipogenesis and decreased lipolysis, which promote fat growth.

Notably, these findings convey converging physiological and molecular mechanisms underlying the correlation between late eating and increased obesity risk.