Relationship between actigraphy-assessed sleep quality and fat mass in college students.

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 ± 3.7 years, BMI 23.1 ± 4.1 kg/m(2) ) for 12 ± 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 = -0.35, P < 0.01] and for free days in men (FMI: r = -0.37, P < 0.05). Poor sleep efficiency was associated with less physical activity (r = 0.29, P < 0.05) and impaired HRV in women (r = 0.60, P < 0.05) and with a higher fat intake in men (r = -0.39, 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.

Impact of protein supplementation after bariatric surgery: A randomized controlled double-blind pilot study.

OBJECTIVES: Bariatric patients are at risk of protein deficiency. The aim of this study was to determine possible benefits of postoperative protein supplementation weight reduction, body composition, and protein status. METHODS: Twenty obese patients who underwent bariatric surgery were randomized either to the protein (PRO) group, which received a daily protein supplement over 6 months postoperatively, or to the control (CON) group, which received an isocaloric placebo in a double-blind fashion. Data on protein and energy intake, body weight, body composition, blood proteins, and grip force was collected preinterventionally and at 1, 3, and 6 months postoperatively. RESULTS: In both groups body weight was significantly reduced to a similar extent (after 6 months: PRO group 25.4 ± 7.2%, CON group 20.9 ± 3.9%; intergroup comparison P > 0.05). Protein intake was steadily increased in the PRO group, but not in the CON group, and reached maximum at month 6 (25.4 ± 3.7% of energy intake versus 15.8 ± 4.4%; P < 0.001). In the PRO group, body fat mass loss was higher than that in the CON group (79% of absolute weight loss versus 73%; P = 0.02) while lean body mass loss was less pronounced (21% versus 27%, P = 0.05). Blood proteins and grip force did not differ at any time point between the two groups. CONCLUSIONS: The present study suggests that protein supplementation after bariatric surgery improves body composition by enhancing loss of body fat mass and reducing loss of lean body mass within the 6 months follow up.

Endocrine determinants of changes in insulin sensitivity and insulin secretion during a weight cycle in healthy men.

OBJECTIVE: Changes 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. METHODS: In 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. RESULTS: IS 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. CONCLUSION: Weight 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 REGISTRATION: ClinicalTrials.gov NCT01737034.