The obesity epidemic in the United States is due to an imbalance between energy intake and expenditure. Energy balance is controlled by a hormone system. This hormone system transfers information from the body to the brain. A reduction in sleep can affect the hormone system’s control on energy balance. Previous research has found higher ghrelin concentrations (a hormone that increases hunger) and lower leptin (a hormone that reduces hunger) is associated with less sleep. Furthermore, parts of the brain that have a role in appetite and the motivation to eat have been found to be more active to food under reduced sleep.
This study was conducted to determine if the brain responds to food images after a period of restricted sleep (4 hours/night) is more evident than after a period of habitual sleep (9 hours/night).
26 participants were recruited for the study. Eligibility requirements were 30-45 years, body mass index of 22-26, and maintenance of stable weight for 3 or more months. Some exclusionary criteria were sleep disorders, eating disorders, diabetes, smoking, and frequent caffeine intake.
In phase 1, participants were randomly assigned to 6 days of habitual sleep or restricted sleep. Phase 2 followed after a 3 week break period, when the participants completed the opposite sleep condition. The participants were fed a controlled diet during the first 4 days and freedom to eat as they liked on days 5-6. They had freedom to exercise throughout the study. On day 6 the participants were screened for brain activity using a technique called fMRI. They were shown timed blocks of food and nonfood images, such as fruit, doughnuts, and office supplies.
Changes in brain activity due to restricted sleep activated regions linked to motivation, desire, and appetite. Participants with restricted sleep displayed more brain activity in response to food images than participants with habitual sleep. A greater intake from snacks and food overall was found after conditions of restricted sleep.
The researchers did not differentiate between high and low calorie foods while other studies have found that high calorie foods may be preferred by subjects after sleep restriction. In addition, the researchers used participants that were all relatively normal weight. Whether sleep restriction causes different brain responses to food between lean and obese individuals is not known.
Reduced sleep may lead to changes in brain activity that signals decreased energy stores in the body and lead to overall increase in appetite, desire, and motivation to eat.
The report is titled “Sleep Restriction Leads to Increased Activation of Brain Regions Sensitive to Food Stimuli.” It is in the April 2012 issue of the American Journal of Clinical Nutrition (volume 95, pages 818-824). The authors are M. Pierre-St-Onge, A. McReynolds, Z. Trivedi, A. Roberts, M. Sy, and J. Hirsch.
Written by Tiffany Geoffroy, Dept. Nutritional Sciences, Rutgers University-NewBrunswick Edited by SA Shapses PhD, RD