November 2012

Partial Sleep Deprivation and Energy Balance in Adults: An Emerging Issue for Consideration by Dietetics Practitioners

This month’s Academy article is a review of literature focusing on effects of sleep deprivation on weight status. Countless epidemiologic studies have found a correlation between sleep duration and adiposity over past decades. Particularly striking statistics on obesity and sleep duration of American adults are cause for curiosity. Over 35% of adults are obese and 28% of adults sleep less than 6 hours per night; both obesity rates and the number of Americans sleeping less than 6 hours per night have increased over the past 30 years.

Many pathways exist in which sleep deprivation may affect body weight and/or body composition, including decreased energy expenditure, increased energy intake (possibly due to hormonal disruption), and altered substrate utilization. Possible pathways are depicted in the figure below.

 

                 Ghrelin is a hormone that is secreted into the stomach and stimulates appetite whereas leptin promotes satiety. Increased appetite is a common complaint among dieters, for which these appetite hormones may be responsible. Leptin decreases with energy restriction and ghrelin increases with weight loss, which may make weight loss continually more difficult. The effect of sleep deprivation on leptin and ghrelin has been investigated in the reviewed studies.

               Cross-sectional and prospective studies have consistently demonstrated a relationship between obesity and sleep duration; however, intervention studies that test specific mechanisms within this relationship have produced profound and sometimes conflicting results. For instance, one study found that ghrelin increased and leptin decreased significantly for those sleeping 4 hours versus 10 hours whereas another study found no different in leptin and ghrelin concentrations for those sleeping 4.5 versus 7 hours. Other results include increased consumption of kcal and proportion of kcal as fat and saturated fat among sleep deprived participants. Also, sleep deprived participants reported less activity although another study reported no differences in total energy expenditure and resting energy expenditure. Cortisol levels (the stress hormone that encourages fat storage) increased among the sleep deprived as well. There are conflicting results on the effect of sleep deprivation on glucose metabolism. Finally, dieters that are sleep deprived lost proportionally more fat free mass than those who were not.

Shlisky, J. D., Hartman, T. J., Kris-Etherton, P. M., Rogers, C. J., Sharkey, N. A., & Nickols-Richardson, S. M. (2012). Partial Sleep Deprivation and Energy Balance in Adults: An Emerging Issue for Consideration by Dietetics Practitioners. Journal of the Academy of Nutrition and Dietetics, 112(11), 1785-1797.

  

         The Association of Sleep Duration with Adolescents' Fat and Carbohydrate Consumption

              The following is a cross-sectional study from the Cleveland Children's Sleep and Health Study published by a past Case Western Reserve University dietetics student. The results for adolescents are similar to the results from the studies on adults reviewed above. This is an example of what a investigative study into the affects of sleep duration entails.

              Weiss and Redline examined the sleep patterns and nutrient intakes of 240 16-19 year old adolescents using overnight polysomnography and 24-hr food recalls. The mean BMI of study participants was 23.1 kg/m², with an average nightly sleep of 7.55±1.14 hours. Adolescents sleeping less than 8 hours per night (defined as short sleep duration for this study) consumed more kilocalories than those sleeping greater than 8 hours per night (means: 1,968 vs. 1,917; P=0.009). Not only did total kilocalorie intake increase for those with short sleep durations, but the proportion of kilocalories consumed from fat increased (35.9% ± 6.7% vs. 33.2% ±6.9%; P=0.004) and that from carbohydrates decreased (49.6% ± 8.2% vs. 53.5% ± 8.3%; P=0.001). Data suggest that the association between short sleep and pro-obesogenic dietary habits may be stronger in girls than boys. Physical activity was not controlled for in this study.

Weiss, A., Xu, F., Storfer-Isser, A., Thomas, A., Ievers-Landis, C. E., & Redline, S. (2010). The association of sleep duration with adolescents' fat and carbohydrate consumption. Sleep, 33(9), 1201.

Link to the study: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2938861/