Eating late increases hunger, reduces calories burned, and changes adipose tissue

Obesity affects approximately 42 percent of US adults and contributes to chronic diseases including diabetes, cancer and other diseases. While popular healthy diet mantras advise against midnight snacking, few studies have comprehensively investigated the simultaneous effects of late eating on three major contributors to body weight regulation and thus obesity risk: regulation of caloric intake, calorie burn, and molecular changes in adipose tissue. . A new study by investigators at Brigham and Women’s Hospital, a founding member of the Mass General Brigham Health System, found that what we eat significantly affects our energy expenditure, appetite and molecular pathways in adipose tissue. Their results are published in Cellular metabolism.

“We wanted to test the mechanisms that might explain why late eating increases the risk of obesity,” explained senior author Frank AJL Scheer, Ph.D. “Previous research by us and others has shown that eating late is associated with an increased risk of obesity body fat, and worsening weight loss success. We wanted to understand why.”

“In this study, we asked, ‘Does the time we eat matter, all else held constant?'” said first author Nina Vujovich, Ph.D., research fellow in the Medical Chronobiology Program in the Brigham Department of Sleep and Sleep. Circadian disorders. “And we found that eating four hours later has a significant effect on our hunger levels, how we burn calories after eating, and how we store fat.”

Vujovich, Scheer and their team studied 16 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 another with exactly the same meals, each scheduled approximately four hours later in the day. During the last two to three weeks before each laboratory protocol, participants maintained a fixed sleep-wake schedule, and during the last three days before entering the laboratory, they strictly followed the same diets and eating schedules at home. In the lab, participants regularly documented their hunger and appetite, frequently gave small blood samples throughout the day, took their body temperature, and energy consumption is measured. To determine how the timing of meals affects the molecular pathways involved in adipogenesis, or how the body stores fat, the researchers collected biopsies adipose tissue from a subset of participants during laboratory testing in both the early and late meal protocols to enable comparison of gene expression patterns/levels between the two feeding conditions.

The results showed that eating late has a profound effect on hunger and the appetite-regulating hormones leptin and ghrelin, which influence our desire to eat. Specifically, levels of the satiety-signalling hormone leptin were reduced over 24 hours in the late meal compared to the early meal. When participants ate later, they also burned calories at a slower rate and showed adipose tissue gene expression toward increased adipogenesis and decreased lipolysis, which promote fat growth. Notably, these findings convey converging physiological and molecular mechanisms underlying the relationship between late eating and increased risk of obesity.

Vujovich explains that not only do these findings align with a large body of research that suggests eating later can increase the likelihood of developing obesity, but they shed new light on how this might happen. Using a randomized crossover trial and tightly controlling behavioral and environmental factors such as physical activity, posture, sleep and exposure to light, researchers were able to detect changes in various control systems involved in energy balance, which shows how our bodies use the food we consume.

In future studies, Sher’s team aims to recruit more women to increase the generalizability of their findings to the wider population. While this study’s cohort included only five participants, the study was designed to control for menstrual phase, reducing confounding but complicating recruitment of women. Looking ahead, Scheer and Vujovich are also interested in better understanding the impact of the relationship between meal times and sleep on energy balance.

“This study shows the effects of eating late versus early. Here, we teased out these effects while controlling for confounding variables such as caloric intake, physical activitysleep and exposure to light, but in real life many of these factors can be affected by meal timing,” said Shire. “In larger studies where tight control of all these factors is not possible, we should at least consider how other behavioral and environmental variables modify these underlying biological pathways risk of obesity.”