It is well established that getting less than eight hours of sleep (more for children and adolescents) is associated with an increased risk of obesity and obesity-related diseases, like type 2 diabetes. The link between sleep and obesity is a hot topic among researchers with a recent review published in Lancet Diabetes and Endocrinology and a study published in the Journal of Pediatrics. Both add to the large body of evidence showing how inadequate sleep negatively affects the health of adults as well as adolescents.

Several reasons why poor sleep contributes to obesity and obesity-related disease have been experimentally determined. Sleep loss has been shown to promote a diabetes-like state, even in healthy individuals, by reducing insulin sensitivity. Food intake is consistently greater among those with inadequate sleep, possibly due to abnormal concentrations of hormones which regulate hunger. Decreased physical activity due to inadequate sleep has also been suggested as a potential cause of the increased risk of obesity; however, study results have been mixed.

A new study published by the Public Library of Science (PLOS One) suggests that inadequate morning sunlight may be a contributing cause as well. In this study, the calorie intake, activity, sleep schedule, and light exposure of 54 individuals was meticulously tracked for seven days. When controlling for the other variables, individuals that received the majority of their exposure to bright light in the morning had lower weights on average. The researchers hypothesized that the blue light of morning favorably influences levels of melatonin – the hormone that regulates your sleep/wake cycle.

The researchers found that the largest predictor of bright light exposure in the morning was midpoint of sleep. Those with an early midpoint of sleep – meaning they generally went to bed earlier and woke up earlier – on average were exposed to bright light earlier in the day. While the results of this study should be viewed as preliminary, a general recommendation from this study may be to get to bed early and wake with the sun. This may promote more exposure to morning sunlight which may help promote a healthy weight.

By Ron Beckstrom, MS, RD, HFS
Nutrition Specialist

This article is for nutrition information purposes only and does not constitute medical advice. Always seek the advice of a qualified health provider with any health concerns you may have. The information in this article is not intended to promote any specific product, or for the prevention or treatment of any disease.

Articles cited:

  • Iglayreger HB, Peterson MD, Liu D1, Parker CA, Woolford SJ, Sallinen Gafka BJ, Hassan F, Gordon PM. Sleep Duration Predicts Cardiometabolic Risk in Obese Adolescents. J Pediatr. 2014 Feb 28. pii: S0022-3476(14)00062-6.
  • Reid KJ, Santostasi G, Baron KG, Wilson J, Kang J, Zee PC. Timing and intensity of light correlate with body weight in adults. PLoS One. 2014 Apr 2;9(4):e92251.
  • Schmid SM, Hallshmid M, Schultes B. The metabolic burden of sleep loss. Lancet Diabetes and Endocrinol. 2014 Mar 25. Early online publication available at: