Late-night eating habits tied to slower calorie burn, increased appetite

A common perception around meal timing and human health is that it’s best to steer clear of late-night dinners and midnight snacking, and a new study has offered some compelling insights into the reasons why. The study compared late-night eating to a regular eating schedule and found some marked differences in terms of obesity risk, revealing effects on appetite, formation of fat tissue and energy expenditure throughout the day.

Led by scientists at the Brigham and Women’s Hospital, the new study sought to comprehensively examine some of the bodily effects of late-night eating. Some interesting studies have shed light on the relationship between meal-timing and human health, including some that highlight the anti-aging potential of daytime eating, and one last month that showed how a big breakfast can help suppress appetite in obese subjects.

In bringing their expertise to the topic, the authors of the new study were focused on three key factors in body weight: calorie intake, calories burnt and molecular changes in fat tissue.

“We wanted to test the mechanisms that may explain why late eating increases obesity risk,” explained senior author Frank A. J. L. Scheer. “Previous research by us and others had shown that late eating is associated with increased obesity risk, increased body fat, and impaired weight loss success. We wanted to understand why.”

To find answers, the scientists enlisted 16 obese or overweight subjects, who completed two in-laboratory eating schedules as part of a randomized crossover study tightly controlled for factors like posture, sleep, light exposure and physical activity. Both eating schedules featured the exact same meals, except one protocol involved eating them about four hours later in the day.

Throughout, the subjects provided regular blood samples, documented their hunger and appetite levels and had their body temperature and energy expenditure monitored. The scientists also collected biopsies of fat tissue to track how the differing meal times shaped molecular pathways associated with fat formation. And these measurements unearthed some compelling differences between the two eating schedules.

Eating later was found to alter the appetite-regulating hormone ghrelin and lower levels of the hormone leptin, which signals to the brain that we are full, increasing hunger levels during waking hours. When the subjects ate later in the day, they also burned calories more slowly and exhibited altered gene expression in fat tissue. These changes favored the storage of lipids, promoting fat growth.

“In this study, we asked, ‘Does the time that we eat matter when everything else is kept consistent?’” said first author Nina Vujovic. “And we found that eating four hours later makes a significant difference for our hunger levels, the way we burn calories after we eat, and the way we store fat.”

The research was published in the journal Cell Metabolism. 

Source: Brigham and Women’s Hospital