Morning and Evening Blue-Enriched Light Exposure Alters Metabolic Function in Normal Weight Adults

• Published in: PloS one Vol. 11; no. 5; p. e0155601
• Main Authors: Cheung, Ivy N, Zee, Phyllis C, Shalman, Dov, Malkani, Roneil G, Kang, Joseph, Reid, Kathryn J
• Format: Journal Article
• Language: English
• Published: United States Public Library of Science 18-05-2016; Public Library of Science (PLoS)
• Subjects: Acute effects; Adolescent; Adult; Adults; Analysis; Appetite; Arousal; Biology and Life Sciences; Body mass index; Body Weight; Circadian rhythm; Cortisol; Darkness; Energy Metabolism; Engineering and Technology; Enrichment; Environmental Exposure; Environmental regulations; Evening; Exposure; Feeding behavior; Female; Food; Genetic aspects; Ghrelin; Ghrelin - metabolism; Glucose; Glucose metabolism; Health care; Hormones; Humans; Hunger; Hydrocortisone - metabolism; Insulin; Insulin resistance; Leptin; Leptin - metabolism; Light; Male; Medicine and Health Sciences; Melatonin; Metabolism; Middle Aged; Morning; Neurology; Obesity; Photoperiodism; Physical Sciences; Physiological aspects; Physiology; Preventive medicine; Shift work; Sleep; Sleep and wakefulness; Sleepiness; Studies; Weight control; Weight reduction; Young Adult; United States; United States > US; Illinois; Chicago Illinois
• ISSN: 1932-6203; 1932-6203
• DOI: 10.1371/journal.pone.0155601

Increasing evidence points to associations between light-dark exposure patterns, feeding behavior, and metabolism. This study aimed to determine the acute effects of 3 hours of morning versus evening blue-enriched light exposure compared to dim light on hunger, metabolic function, and physiological arousal. Nineteen healthy adults completed this 4-day inpatient protocol under dim light conditions (<20lux). Participants were randomized to 3 hours of blue-enriched light exposure on Day 3 starting either 0.5 hours after wake (n = 9; morning group) or 10.5 hours after wake (n = 10; evening group). All participants remained in dim light on Day 2 to serve as their baseline. Subjective hunger and sleepiness scales were collected hourly. Blood was sampled at 30-minute intervals for 4 hours in association with the light exposure period for glucose, insulin, cortisol, leptin, and ghrelin. Homeostatic model assessment of insulin resistance (HOMA-IR) and area under the curve (AUC) for insulin, glucose, HOMA-IR and cortisol were calculated. Comparisons relative to baseline were done using t-tests and repeated measures ANOVAs. In both the morning and evening groups, insulin total area, HOMA-IR, and HOMA-IR AUC were increased and subjective sleepiness was reduced with blue-enriched light compared to dim light. The evening group, but not the morning group, had significantly higher glucose peak value during blue-enriched light exposure compared to dim light. There were no other significant differences between the morning or the evening groups in response to blue-enriched light exposure. Blue-enriched light exposure acutely alters glucose metabolism and sleepiness, however the mechanisms behind this relationship and its impacts on hunger and appetite regulation remain unclear. These results provide further support for a role of environmental light exposure in the regulation of metabolism.