Late, but Not Early, Night Sleep Loss Compromises Neuroendocrine Appetite Regulation and the Desire for Food.

OBJECTIVE: There is evidence that reduced sleep duration increases hunger, appetite, and food intake, leading to metabolic diseases, such as type 2 diabetes and obesity. However, the impact of sleep timing, irrespective of its duration and on the regulation of hunger and appetite, is less clear. We aimed to evaluate the impact of sleep loss during the late vs. early part of the night on the regulation of hunger, appetite, and desire for food. METHODS: Fifteen normal-weight ([mean ± SEM] body-mass index: 23.3 ± 0.4 kg/m2) healthy men were studied in a randomized, balanced, crossover design, including two conditions of sleep loss, i.e., 4 h sleep during the first night-half ('late-night sleep loss'), 4 h sleep during the second night-half ('early-night sleep loss'), and a control condition with 8h sleep ('regular sleep'), respectively. Feelings of hunger and appetite were assessed through visual analogue scales, and plasma ghrelin and leptin were measured from blood samples taken before, during, and after night-time sleep. RESULTS: Ghrelin and feelings of hunger and appetite, as well as the desire for food, were increased after 'late-night sleep loss', but not 'early-night sleep loss', whereas leptin remained unaffected by the timing of sleep loss. CONCLUSIONS: Our data indicate that timing of sleep restriction modulates the effects of acute sleep loss on ghrelin and appetite regulation in healthy men. 'Late-night sleep loss' might be a risk factor for metabolic diseases, such as obesity and type 2 diabetes. Thereby, our findings highlight the metabolic relevance of chronobiological sleep timing.

Chronobiological aspects of sleep restriction modulate subsequent spontaneous physical activity.

PURPOSE: First evidence suggests that chronobiological aspects of sleep restriction affect metabolic conditions. Our aim was to investigate whether spontaneous free-living physical activity likewise is affected by chronobiological timing of short sleep. METHODS: In an experimental randomized, balanced cross-over design, eleven healthy, normal-weight (BMI: 23.9 ± 0.4 kg/m2) men were evaluated. Physical activity was assessed by tri-axial wrist actigraphy after (i) four-hour sleep during the first night-half of the night ('late night sleep loss'), (ii) four-hour sleep during the second night-half ('early night sleep loss'), and (iii) eight-hour regular sleep ('regular sleep'), from 7:00 to 24:00 (17 h). Feelings of tiredness and activity were measured by semi-quantitative questionnaires. RESULTS: Physical activity differed between sleep conditions (P < 0.05) with the lowest physical activity after 'late night sleep loss'. Accordingly, less time was spent in high-intensity physical activity after 'late night sleep loss' as compared to the 'early night sleep loss' and 'regular sleep' conditions (both P < 0.05). Perceived feelings of tiredness were higher after both short sleep conditions as compared to 'regular sleep' (both P < 0.05). CONCLUSIONS: Sleep restriction during the second half of the night elicits stronger effects on spontaneous physical activity than sleep restriction during the first half of the night despite identical sleep duration, but the impact of longer period awake needs to be evaluated in further research. In sum, these data indicate that not only short sleep per se but also chronobiological aspects modulate physical activity pattern.