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Objective: Only a few studies have used objective measurements to investigate the relationship between sleep quality and obesity. These studies showed controversial results. Methods: Sleep efficiency was measured by Actiwatch 2 in 132 healthy students (age 23.3 6 3.7 years, BMI 23.1 6 4.1 kg/m 2 ) for 12 6 3 nights, differentiating between work and free days. Physical activity, dietary habits, and autonomic function (heart rate variability, HRV) were analyzed as potential determinants of sleep quality and its relationship with body composition. Results: Sleep efficiency was 87.0% in women and 84.9% in men (P < 0.05) and was higher at free days when compared to work days in women (P < 0.05). Lower sleep efficiency was associated with a higher fat mass. This was true for sleep efficiency on work days in women [fat mass index (FMI): r 5 20.35, P < 0.01] and for free days in men (FMI: r 5 20.37, P < 0.05). Poor sleep efficiency was associated with less physical activity (r 5 0.29, P < 0.05) and impaired HRV in women (r 5 0.60, P < 0.05) and with a higher fat intake in men (r 5 20.39, P < 0.05). Conclusions: Poor sleep efficiency was associated with higher fat mass. The relationship between sleep quality and fat mass differs between work and free days and may be explained by physical activity and autonomic function in women and dietary habits in men.

Compared with high-GI SSB, 7-day consumption of beverages sweetened with low-GI isomaltulose had beneficial effects on inactivity-induced impairment of glucose metabolism without effecting fuel selection.

ObjectiveChanges in insulin sensitivity (IS) and insulin secretion occur with perturbations in energy balance and glycemic load (GL) of the diet that may precede the development of insulin resistance and hyperinsulinemia. Determinants of changes in IS and insulin secretion with weight cycling in non-obese healthy subjects remain unclear.MethodsIn a 6wk controlled 2-stage randomized dietary intervention 32 healthy men (26±4y, BMI: 24±2kg/m2) followed 1wk of overfeeding (OF), 3wks of caloric restriction (CR) containing either 50% or 65% carbohydrate (CHO) and 2wks of refeeding (RF) with the same amount of CHO but either low or high glycaemic index at ±50% energy requirement. Measures of IS (basal: HOMA-index, postprandial: Matsuda-ISI), insulin secretion (early: Stumvoll-index, total: tAUC-insulin/tAUC-glucose) and potential endocrine determinants (ghrelin, leptin, adiponectin, thyroid hormone levels, 24h-urinary catecholamine excretion) were assessed.ResultsIS improved and insulin secretion decreased due to CR and normalized upon RF. Weight loss-induced improvements in basal and postprandial IS were associated with decreases in leptin and increases in ghrelin levels, respectively (r = 0.36 and r = 0.62, p<0.05). Weight regain-induced decrease in postprandial IS correlated with increases in adiponectin, fT3, TSH, GL of the diet and a decrease in ghrelin levels (r-values between -0.40 and 0.83, p<0.05) whereas increases in early and total insulin secretion were associated with a decrease in leptin/adiponectin-ratio (r = -0.52 and r = -0.46, p<0.05) and a decrease in fT4 (r = -0.38, p<0.05 for total insulin secretion only). After controlling for GL associations between RF-induced decrease in postprandial IS and increases in fT3 and TSH levels were no longer significant.ConclusionWeight cycling induced changes in IS and insulin secretion were associated with changes in all measured hormones, except for catecholamine excretion. While leptin, adiponectin and ghrelin seem to be the major endocrine determinants of IS, leptin/adiponectin-ratio and fT4 levels may impact changes in insulin secretion with weight cycling.Trial RegistrationClinicalTrials.gov NCT01737034

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