Researchers looked at the effects of sleep deprivation in healthy volunteers to investigate what underlies the link between lack of sleep and obesity.
There is a well-established link between lack of sleep and obesity, as the length of sleep is correlated with changes in body mass index and body fat percentage, which are measures of obesity. Some researchers suggest that sleep deprivation disturbs the balance of appetite hormones, whilst others propose that it causes changes in the brain’s reward systems. Both of these mechanisms could lead to overeating and a higher risk of obesity.
To investigate what underlies the link between lack of sleep and obesity, researchers in Germany looked at the effects of sleep deprivation in healthy volunteers. They recently reported their findings in the Journal of Neuroscience.
Underlying mechanism could be due to hormonal or brain changes
The researchers recruited 32 healthy, normal-weight, male volunteers. After an initial physical assessment, the volunteers visited the laboratory on two separate evenings. At the experimental sessions, all volunteers were fed a calorie-controlled evening meal, following which half of the group was sent home to sleep normally and the other half stayed at the study center were kept awake all night. The following morning all volunteers attended the laboratory for testing.
Blood samples were taken at the start (evening) and end (morning) of the experimental session to measure appetite hormone levels. In the morning, all volunteers participated in a decision-making assessment involving valuing and choosing food or non-food rewards, whilst undergoing a brain scan.
The researchers found that appetite hormone levels were not affected by sleep deprivation. However, in the decision-making assessment the sleep-deprived volunteers placed more value on food items than non-food items. The brain scans reflected these behavioral differences, with increased activity in the reward-processing area of the brain in the sleep-deprived volunteers.
Brain reward areas show increased activity after one night’s sleep loss
The researchers concluded that there is increased food valuation after sleep deprivation, and this is due to changes in the brain’s reward system rather than hormonal changes. Brain scans revealed changes in the brain reward system areas after just one night’s sleep loss. These changes could lead to overeating, weight gain and obesity.
Written by Julie McShane, Medical Writer
- Rihm JS, Menz MM, Schultz H, et al. Sleep deprivation selectively up-regulates an amygdala-hypothalamic circuit involved in food reward. J Neurosci 2018;10.1523/JNEUROSCI.0250-18.2018
- Press release. Society for Neuroscience. 17 Dec 2018. “Unraveling the link between obesity and sleep.” https://www.eurekalert.org/pub_releases/2018-12/sfn-utl121118.php