Oct. 4 (UPI) -- It may be time to forget the late supper or midnight snack. New research suggests that eating late in the evening may increase hunger, decrease calories burned and cause molecular changes in fat tissue -- which together may heighten the risk of obesity.
The researchers, led by Brigham and Women's Hospital in Boston, said in their paper that they rigorously controlled for nutrient intake, physical activity, sleep and light exposure among the study's participants.
They found that shifting to eating four hours later makes a significant difference in hunger levels, the way the body burns calories after eating and the way in which body fat is stored, even when everything except food timing is kept consistent.
Their findings from the small study appeared Tuesday in the journal Cell Metabolism.
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"We wanted to test the mechanisms that may explain why late eating increases obesity risk," Frank A. J. L. Scheer, the study's senior author and director of the Medical Chronobiology Program in the Brigham's Division of Sleep and Circadian Disorders, said in a news release.
Scheer said previous research at Brigham and Women's and elsewhere has shown that late eating "is associated with increased obesity risk, increased body fat and impaired weight loss success. We wanted to understand why."
Nationwide, roughly 42% of the adult population is obese, a condition that may contribute to the onset of chronic diseases, including diabetes and cancer, the investigators said.
Globally, obesity is an epidemic affecting an estimated 650 million adults, they added.
The research team studied 16 patients with a body mass index, or 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 last meal scheduled about four hours later in the day.
Under the experimental design, starting on Day 3 in the late eating protocol, the participants delayed their three meals to 1:10 p.m., 5:20 p.m. and 9:30 p.m. They had the same three meals as under the early eating protocol, but they were delayed by 250 minutes, or roughly four hours, Scheer told UPI in an email.
In the few weeks before starting each of the protocols, the study's participants kept 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, the release said.
In the lab, they 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, the investigators collected biopsies of fat tissue from a subset of participants during laboratory testing in both the early and late eating protocols.
They found that eating later significantly affected hunger and the appetite-regulating hormones leptin and ghrelin. Levels of leptin, which signals the body is sated, were decreased for 24 hours in the late eating condition compared to the early eating condition.
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, the release said.
So, the investigators said, they found converging physiological and molecular mechanisms underlying the correlation between late eating and increased obesity risk.
They said their findings are consistent with a large body of research suggesting that eating later may increase a person's likelihood of becoming obese -- and shed new light on how this may occur.
