Biological Clocks: Late-Night Eating Increases Obesity Risk in Adolescents

“Biological clocks (circadian rhythms) may have a link between eating habits and weight gain in teenagers,” study finds. Calorie intake later in the day can increase the risk of obesity. Obesity is a complex chronic disease caused by many factors. A new study from researchers at the Warren Alpert Medical School of Brown University and Mass General Brigham reveals a relationship between circadian rhythms and eating habits in adolescents. Eating habits in this age group are crucial and influence their lifelong health. The results are published in the Proceedings of the National Academy of Sciences.

Advertisement

Biological clock and Late-Night Eating

The study found that adolescents whose weight was classified as “overweight” or “obese” consumed more calories later in the day compared to participants with healthy weights. The results demonstrate that circadian rhythms play an important role in explaining later caloric intake in individuals at risk for obesity, said lead investigator Mary Carskadon, a professor of psychiatry and human behavior at Brown’s Medical School.

“The critical nature of adolescent development to set the stage for a lifetime of health highlights the need to understand the roles played by sleep/wake and circadian timing processes for eating behavior,” said Carskadon, who also directs the Bradley Hospital Sleep Research Laboratory. “The knowledge gained here opens a door to potential interventions that can enhance teen health moving forward.”

The circadian system is composed of trillions of “clocks” present in virtually all organs, tissues, and cells, which prepares biology and behavior to adapt to the changing demands across the day/night cycle. The influence of the circadian system is known to differ between people due to a combination of genetic, behavioral, and environmental factors.

Advertisement

Study on Teen Eating Habits

Previous studies have analyzed sleeping and eating behavior using measures of self-reported hunger and other variables, said study author David Barker, an associate professor of psychiatry and human behavior (research) at Brown. Some factors that set this study apart, Barker said, were the meticulous measuring of food before and after meals and the fact that environmental and behavioral influences were controlled for while the participants remained in the lab.

Fifty-one volunteers between the ages of 12 and 18 participated in the study, which was conducted at the Bradley Hospital Sleep Research Laboratory. Participants were divided into three groups based on body mass index. They were placed on 28-hour sleep and wake cycles — slightly longer than a typical 24-hour day — and stayed in a controlled dim-light setting while awake and in complete darkness during sleep.

Participants remained in the same space throughout the study, which lasted for 11 days and 10 nights. To control for outside influences on circadian rhythm, researchers removed all external time cues from the lab’s environment, including clocks and access to natural light.

Participants received six opportunities to eat at fixed times across the wake episode, with a standardized menu, and could consume as much food during the meal as they wanted. Researchers tracked the food that was eaten as well as caloric intake. During the day, they were monitored by student research apprentices from Brown University and other institutions, who offered opportunities to join in a variety of activities including making crafts, watching movies (with screen lights dimmed), and playing social games.

Advertisement

Why We Eat More at Night

The results showed that changes in the circadian system throughout the day and night significantly influenced food consumption. In all three groups, food intake peaked in the late afternoon and early evening and was lowest in the morning, even after accounting for behavioral and environmental factors, demonstrating that the body’s biological clock directly impacts how much people eat at different times of the day.

Adolescents in the obesity and overweight groups consumed significantly more calories in the circadian evening compared to those in the healthy weight group. Researchers found no significant differences in total sleep time between or within the groups across sleep cycles.

According to study author Frank Scheer, director of the Medical Chronobiology Program at Brigham and Women’s Hospital, it was already well-known that the circadian system affects hunger and metabolism. What remained unclear, he said, was whether the circadian system — when isolated from influences of environmental and behavioral cycles, including light, sleep, and activity cycles — directly influences food consumption.

Future studies are needed to determine whether affecting the circadian control of food intake contributes to weight changes if weight changes impact the circadian control of food intake, or a combination of the two. Carskadon said that the findings like those from the study could inform clinicians counseling adolescents on ways to manage their weight.

“For example, the influence of circadian timing could be influenced by excluding light late in the day and enhancing bright light in the morning, especially while exercising,” Carskadon said. “That might help pull the rhythms to a better place — and also create healthy habits.”

With future research, the team aims to gain a deeper understanding of the interactions between the circadian system, diet, and metabolism, as well as the mechanisms underlying these relationships, and the implications for developing timed dietary interventions to improve health.

Source-Eurekalert