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Study Links Circadian Rhythms to Eating Habits and Obesity in Adolescents
The development of obesity is a multifaceted issue, influenced by a variety of factors. Recent research has made connections among sleep patterns, dietary habits, and weight gain, but the specific impact of the circadian system—or biological clock—on eating behaviors remains uncertain.
New findings from the Warren Alpert Medical School of Brown University in collaboration with Mass General Brigham have unveiled a significant connection between circadian rhythms, dietary habits, and weight in adolescents. This age group is particularly susceptible to developments in their eating behaviors that can affect their long-term health. The research indicates that adolescents categorized as “overweight” or “obese” tend to consume more calories during the later parts of the day compared to their healthier-weight peers.
According to Mary Carskadon, the study’s lead investigator and a professor of psychiatry and human behavior at Brown University, these results highlight the significance of circadian rhythms in understanding caloric consumption, particularly among those at risk for obesity. “Adolescent development is crucial for establishing a trajectory of health,” she noted, emphasizing the importance of comprehending how sleep/wake cycles and circadian timing influence eating behavior. The research opens pathways for potential interventions aimed at promoting healthier outcomes for teens.
The findings were documented in the Proceedings of the National Academy of Sciences.
Understanding Circadian Influence
The circadian system consists of trillions of biological “clocks” situated within virtually every organ and tissue, which help regulate biological and behavioral adjustments to the day/night cycle. Individual variations in the circadian influence stem from a complex interplay of genetic, behavioral, and environmental components.
Past research has typically utilized subjective reports on hunger and eating behavior. However, David Barker, an associate professor at Brown who contributed to the study, pointed out that the current research distinguished itself by rigorously measuring food before and after meals while isolating environmental and behavioral factors through a controlled lab setting.
The study included 51 adolescents aged 12 to 18, all recruited from the Bradley Hospital Sleep Research Laboratory. Participants were grouped according to their body mass index and subjected to a 28-hour sleep/wake cycle, which is more extended than the standard 24 hours, while being placed in a dimly lit environment during wakefulness and complete darkness while sleeping.
Throughout the 11-day experiment, all external time cues—including clocks and natural light—were eliminated to maintain a controlled environment.Participants were given six opportunities to eat at fixed intervals, with a standardized menu allowing for unlimited quantity during meals. Additionally, they were monitored by researchers and provided with various engagement activities to maintain a consistent social environment.
Results revealed that food intake rose significantly during the late afternoon and evening across all participant groups, while morning consumption proved to be the lowest. This pattern persisted even after controlling for various behavioral and environmental variables, indicating that the biological clock plays a critical role in dictating eating times.
Notably, adolescents identified as overweight or obese exhibited considerably higher caloric intake during evening hours compared to those with healthy weights. However, researchers observed no significant variations in total sleep duration among the different weight categories throughout the study period.
Preliminary Insights into Food Regulation
Frank Scheer, who directs the Medical Chronobiology Program at Brigham and Women’s Hospital, noted that although prior knowledge established the circadian system’s effect on hunger and metabolism, it remained to be determined whether clear regulation of food consumption was directly linked to the internal body clock, particularly when external influences were minimized. “This research is pioneering in demonstrating that our internal clock has a direct regulatory effect on food intake,” Scheer remarked.
Future Directions for Research
Further research is essential to unravel whether manipulating circadian control of food intake can lead to weight changes, if changes in weight have the converse effect on circadian regulation, or if both scenarios coexist.
Carskadon suggested that these insights can aid clinicians advising adolescents on effective weight management strategies. “For instance, curtailing light exposure in the evening while increasing bright light exposure in the morning could potentially align circadian rhythms more favorably, fostering healthier habits,” she explained.
Ongoing investigations will delve deeper into the intricate relationships between the circadian system, dietary choices, and metabolic processes, as well as the scientific mechanisms at play. Such understanding could pave the way for developing targeted dietary interventions aimed at enhancing health outcomes.
This research received financial backing from several institutions, including the National Institute of Diabetes and Digestive and Kidney Diseases, the National Heart, Lung, and Blood Institute, and the National Institutes of Health, as well as support from the COBRE Center focused on Sleep and Circadian Rhythms in Child and Adolescent Mental Health.
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