The Relationship between Sleep Deprivation, Food Motivation, and Energy Intake in Normal-Weight and Obese Females
Objective: Sleep deprivation has been proposed as a potential correlate of obesity, particularly influencing energy intake. Therefore, the purpose of this study was to compare neural indices of attention related to food motivation and energy intake in normal-weight and obese women under two separate sleep conditions: 1) sleep-restricted (<5 >hours) and 2) recommended sleep (~8 hours). This study used a combined cross-over and ex post facto design with condition order counter-balanced. Methods: Twenty-two normal-weight (age=30.9±9.5y, BMI=22.0±1.6 kg/m2) and 18 obese (age=29.7±10.7 y, BMI=36.4±5.3 kg/m2) women completed both sleep conditions. To confirm sleep levels, participants recorded sleep quality and quantity via sleep logs and wore a wrist actigraph. Following each condition, participants reported to the laboratory under the same fed state (energy shake ~10% of total daily needs) to verify they followed the sleep protocol. Subsequently, motivation for food was tested using electroencephalogram (EEG); participants completed a computerized passive-viewing task of food and flowers, while event-related brain potentials (ERPs) were recorded. After EEG testing, participants continued their normal routine but recorded all energy intake using weighed food scales. There were no instructions or limitations on dietary intake. Analyses included P300 and LPP amplitudes in response to picture type, total next day energy intake, and energy intake by several periods of the day. Results: Participants averaged 4.7±0.4 hours of sleep during the sleep-restricted condition and 7.7±0.3 hours during the recommended sleep condition (F=1057.02; P<0.0001). There was no group*condition interaction for next day food motivation (P300: F<2.896, P>0.09; LPP: F<2.967, P>0.093). Next day total energy intake also did not differ by group*condition (F=1.81; P=0.187). When participants were pooled, there was no difference in energy intake by sleep condition (F=0.00; P=0.953). However, when participants’ energy intake was analyzed during the lunch period (following testing to 1:30pm) there was a significant group*condition interaction (F=6.12; P=0.018). The obese women ate significantly more (~300 kcal) during the sleep-deprived condition compared to the recommended condition, whereas the normal-weight women did not. Conclusion: Compared to suggested levels of sleep, sleep restriction and obesity do not influence next day food motivation or total next day energy intake. However, sleep restriction and obesity may influence feeding during certain portions of the day.