Researchers explore what late-night eating does to our waistlines

Are you a midnight snacker? Results of a recent study suggest that eating late at night may increase our hunger levels and impact how our bodies burn calories and store fat.

Researchers at Brigham and Women’s Hospital asked 16 people with a body mass index in the overweight or obese range to complete two protocols: one with a strictly scheduled early meal and another with the same meals scheduled four hours later in the day.

Compared with eating early, the later meals doubled the odds of feeling hungry and significantly increased the odds of wanting to eat more – particularly more starchy and salty foods. Specifically, when participants ate later, levels of the appetite-regulating hormone leptin decreased 16% during awake hours and 10% during eight hours of sleep time.

Burning calories also was more difficult. The participants burned 5% fewer calories when they ate later, and had a lower core body temperature. Eating later also led to multiple molecular reactions that promote the growth of body fat, thus increasing the risk of obesity.

“This study shows the impact of late vs. early eating,” said senior study author Frank Scheer, director of the Medical Chronobiology Program in Brigham’s Division of Sleep and Circadian Disorders. “We isolated these effects by controlling for confounding variables like caloric intake, physical activity, sleep and light exposure, but in real life, many of these factors may themselves be influenced by meal timing.”

The study was published online in the journal Cell Metabolism.