The influence of exercise training dose on fasting acylated ghrelin concentration in older women.

This study investigated if exercise dose affected acylated ghrelin response to exercise training, and how body weight or fat mass changes might affect the responses. Non-obese older women (n = 49) were randomly assigned to 4-month moderate-intensity aerobic exercise of one of two doses (8 or 14 kcal kg-1 body weight weekly). Following exercise training, fasting acylated ghrelin concentrations changed differently between the two groups (p for group × time interaction = 0.050). It decreased in the moderate-dose (Cohen's d = 0.52, p = 0.019), but did not change in the low-dose exercise group. Adjustment for weight or fat changes did not affect these results. Therefore, exercise training dose can have specific effects on acylated ghrelin that are not dependent on weight or fat loss. However, whether the different acylated ghrelin changes are associated with differing degree of subsequent weight maintenance worth further investigation.

The effect of moderate-intensity exercise on nightly variability in objectively measured sleep parameters among older women.

Objective/Background: Exercise training has been demonstrated to beneficially influence mean-level measures of sleep; however, few studies have examined the impact of an exercise intervention on night-to-night variability in sleep. This study investigated whether four months of moderate-intensity exercise impacted night-to-night variability in sleep among older women. Methods: Participants (n = 49) were randomized to one of two moderate-intensity walking programs with different doses of energy expenditure: low-dose (n = 23: 8 kcal/kg of body weight per week) or high-dose (n = 26: 14 kcal/kg of body weight per week). Sleep parameters were assessed objectively via actigraphy at baseline, mid- (2 months), and postintervention (4 months). Nightly variability in each of the sleep parameters was calculated using the seven-day standard deviation (SD) and a coefficient of variation (SD/mean x 100%). Cardiorespiratory fitness (VO2peak) was measured at baseline and postintervention using a graded treadmill test. Results: Both measures of nightly variability demonstrated a borderline to significantly lower amount of night-to-night variability in wake time after sleep onset (WASO) and number of awakenings at postintervention in comparison to baseline (p ≤ 0.05). Higher VO2peak levels at baseline were associated with less time in bed and lower total sleep time variability throughout the exercise intervention (p < 0.05). Conclusion: Overall, participation in moderate-intensity exercise was observed to reduce the amount of nightly variability for WASO and number of awakenings over time in older women.

Effects of moderate sleep restriction during 8-week calorie restriction on lipoprotein particles and glucose metabolism.

STUDY OBJECTIVES: This study examined how glucose, glucose regulatory hormones, insulin sensitivity, and lipoprotein subclass particle concentrations and sizes change with sleep restriction during weight loss elicited by calorie restriction. METHODS: Overweight or obese adults were randomized into an 8-week calorie restriction intervention alone (CR, n = 12; 75% female; body mass index = 31.4 ± 2.9 kg/m2) or combined with sleep restriction (CR+SR, n = 16; 75% female; body mass index = 34.5 ± 3.1 kg/m2). Participants in both groups were given the same instructions to reduce calorie intake. Those in the CR+SR group were instructed to reduce their habitual time-in-bed by 30-90 minutes 5 days each week with 2 ad libitum sleep days. Fasting venous blood samples were collected at pre- and post-intervention. RESULTS: Differential changes were found between the two groups (p = 0.028 for group × time interaction) in glucagon concentration, which decreased in the CR group (p = 0.016) but did not change in CR+SR group. Although changes in mean HDL particle (HDL-P) size and visfatin concentration were not statistically different between groups (p = 0.066 and 0.066 for group×time interaction, respectively), mean HDL-P size decreased only in the CR+SR group (Cohen's d = 0.50, p = 0.022); visfatin concentrations did not change significantly in either group but appeared to decrease in the CR group (Cohen's d = 0.67, p = 0.170) but not in the CR+SR group (Cohen's d = 0.43, p = 0.225). CONCLUSION: These results suggest that moderate sleep restriction, despite the presence of periodic ad libitum sleep, influences lipoprotein subclass particles and glucose regulation in individuals undergoing calorie restriction.Clinical trial registration: ClinicalTrials.gov (NCT02413866, Weight Outlooks by Restriction of Diet and Sleep).

Influence of sleep restriction on weight loss outcomes associated with caloric restriction.

Study Objectives: To examine the effects of moderate sleep restriction (SR) on body weight, body composition, and metabolic variables in individuals undergoing caloric restriction (CR). Methods: Overweight or obese adults were randomized to an 8 week caloric restriction (CR) regimen alone (n = 15) or combined with sleep restriction (CR + SR) (n = 21). All participants were instructed to restrict daily calorie intake to 95 per cent of their measured resting metabolic rate. Participants in the CR + SR group were also instructed to reduce time in bed on five nights and to sleep ad libitum on the other two nights each week. Results: The CR + SR group reduced sleep by 57 ± 36 min per day during SR days and increased sleep by 59 ± 38 min per day during ad libitum sleep days, resulting in a sleep reduction of 169 ± 75 min per week. The CR and CR + SR groups lost similar amounts of weight, lean mass, and fat mass. However, the proportion of total mass lost as fat was significantly greater (p = 0.016) in the CR group. This proportion was greater than body fat percentage at baseline for the CR (p = 0.0035), but not the CR + SR group. Resting respiratory quotient was reduced (p = 0.033) only in CR, and fasting leptin concentration was reduced only in CR + SR (p = 0.029). Conclusions: Approximately 1 hr of SR on five nights a week led to less proportion of fat mass loss in individuals undergoing hypocaloric weight loss, despite similar weight loss. SR may adversely affect changes in body composition and "catch-up" sleep may not completely reverse it. Clinical trial registration: ClinicalTrials.gov (NCT02413866).

Energy expenditure responses to exercise training in older women.

Previous studies have shown inconsistent findings regarding how structured exercise affects energy expenditure (EE). This study was designed to determine the changes in EE and physical activity following exercise training in older women. Nonobese (body mass index = 25.8 ± 3.4 kg·m-2) women (60-75 years, n = 72) completed a 4-month supervised aerobic exercise training of lower- or higher-dose (33.6 and 58.8 kJ·kg-1 body weight weekly, respectively) at 50-55% of heart rate reserve. Total daily EE (TDEE) by the doubly labeled water method, resting metabolic rate (RMR) via indirect calorimetry, and physical activity by accelerometer were determined before and at the end of exercise training. Nonexercise activity thermogenesis (NEAT) was calculated. Following exercise training, the changes in components of TDEE and total physical activity did not differ by group. In the entire sample, TDEE, RMR, NEAT and total physical activity did not change (P > 0.05 for all). However, a significant baseline physical activity × time interaction was found for several of the variables. Data were therefore stratified into tertiles of baseline physical activity. In the high tertile, TDEE remained unchanged, but total physical activity decreased (P = 0.012). In contrast, in the middle and low tertiles, NEAT remained unchanged, and total physical activity increased (P < 0.05 for both). In conclusion, aerobic exercise training did not change TDEE, RMR, NEAT, or total physical activity in this sample of older women. Exercise dose did not, but baseline physical activity levels might, influence EE responses and total physical activity changes.