The Effects of Interrupting Sitting Time on Affect and State Anxiety in Children of Healthy Weight and Overweight: A Randomized Crossover Trial.

PURPOSE: Sedentary time relates to higher anxiety and more negative affect in children. This study assessed whether interrupting sitting over 3 hours is sufficient to influence state anxiety, positive affect, or negative affect, and tested weight status as a moderator. METHODS: Analyses were the second (preplanned) purpose of a larger study. Children (N = 61; age: mean [SD] = 9.5 [1.3]; 43% healthy weight) completed 2 experimental conditions: continuous sitting for 3 hours and sitting for 3 hours interrupted with walking for 3 minutes in every 30 minutes. State anxiety, positive affect, and negative affect were reported at pretest and posttest. Multilevel models for repeated measures assessed whether experimental condition predicted posttest scores. RESULTS: Experimental condition was unrelated to posttest state anxiety or positive affect. Weight status moderated how experimental condition influenced posttest negative affect (P = .003). Negative affect was lower in the children of healthy weight after interrupted sitting (vs continuous sitting; ß = -0.8; 95% confidence interval, -1.5 to 0.0, P = .05), but it was higher in the children with overweight/obesity after interrupted sitting (vs continuous sitting; ß = 0.6; 95% confidence interval, 0.0 to 1.2, P = .06). CONCLUSIONS: Interrupting sitting acutely reduced negative affect in children of healthy weight, but not in children with overweight. Further research is needed to better understand the potential emotional benefits of sitting interruptions in youth.

Quantification of the Capacity for Cold-Induced Thermogenesis in Young Men With and Without Obesity.

OBJECTIVE: Cold exposure increases energy expenditure (EE) and could have a role in combating obesity. To understand this potential, we determined the capacity for cold-induced thermogenesis (CIT), the EE increase above the basal metabolic rate at the individualized coldest tolerable temperature before overt shivering. DESIGN: During a 13-day inpatient protocol, we quantitated the EE of 12 lean men and 9 men with obesity at various randomly ordered ambient temperatures in a room calorimeter. Subjects underwent brown fat imaging after exposure to their coldest tolerable temperature. RESULTS: CIT capacity was 300 ± 218 kcal/d (mean ± SD) or 17 ± 11% in lean men and 125 ± 146 kcal/d or 6 ± 7% in men with obesity (P = 0.01). The temperature below which EE increased, lower critical temperature (Tlc), was warmer in lean men than men with obesity (22.9 ± 1.2 vs 21.1 ± 1.7°C, P = 0.03), but both had similar skin temperature (Tskin) changes and coldest tolerable temperatures. Whereas lean subjects had higher brown fat activity, skeletal muscle activity increased synchronously with CIT beginning at the Tlc in both groups, indicating that muscle is recruited for CIT in parallel with brown fat, not sequentially after nonshivering thermogenesis is maximal. CONCLUSIONS: Despite greater insulation from fat, men with obesity had a narrower range of tolerable cool temperatures available for increasing EE and less capacity for CIT than lean men, likely as a result of greater basal heat production and similar perception to Tskin cooling. Further study of the reduced CIT capacity in men with obesity may inform treatment opportunities for obesity.

Associations of sleep patterns with metabolic syndrome indices, body composition, and energy intake in children and adolescents.

BACKGROUND: Self-reported short sleep duration is associated with greater risk for metabolic syndrome (MetS), obesity, and higher energy intake (EI). However, studies of these associations in children using objective methods are sparse. OBJECTIVES: The study aims to determine the associations for sleep patterns with MetS indices, body composition, and EI using objective measures in children. METHODS: Free-living sleep and physical activity were measured in 125 children (aged 8-17 years, BMI z = 0.57 ± 1.0, 55% female) using wrist-worn actigraphs for 14 nights. Blood pressure, fasting blood levels of lipids, insulin, glucose, waist circumference, and body composition (dual-energy X-ray absorptiometry [DXA]) were obtained during outpatient visits. EI was assessed during an ad libitum buffet meal. RESULTS: Later weekday and weekend bedtimes were associated with higher systolic blood pressure (Ps < 0.05). Sleep duration and bedtime were not significantly associated with other components of MetS, body composition, or EI. Short sleepers (duration less than 7 hours) consumed a greater percentage of carbohydrates than those with adequate (greater than or equal to 7 hours) sleep (P < 0.05). CONCLUSION: Indicators of sleep duration were variably associated with children's eating patterns and risk for chronic disease. Prospective data are needed to determine whether these indicators of sleep quality represent unique or shared risk factors for poor health outcomes.

Effects of Interrupting Sedentary Behavior With Short Bouts of Moderate Physical Activity on Glucose Tolerance in Children With Overweight and Obesity: A Randomized Crossover Trial.

OBJECTIVE: Sedentary children have greater risk of developing abnormalities in glucose homeostasis. We investigated whether interrupting sedentary behavior (sitting) with very short periods of walking would improve glucose metabolism without affecting dietary intake in children with overweight or obesity. We hypothesized that interrupting sitting with short bouts of moderate-intensity walking would decrease insulin area under the curve (AUC) during an oral glucose tolerance test (OGTT) compared with uninterrupted sitting. RESEARCH DESIGN AND METHODS: Overweight/obese (BMI ≥85th percentile) children 7-11 years of age underwent two experimental conditions in random order: prolonged sitting (3 h of continuous sitting) and interrupted sitting (3 min of moderate-intensity walking at 80% of ventilatory threshold every 30 min for 3 h). Insulin, C-peptide, and glucose were measured every 30 min for 3 h during an OGTT. Each session was followed by a buffet meal. Primary outcomes were differences in OGTT hormones and substrates and in buffet meal intake by condition. RESULTS: Among 35 children with complete data, mixed-model results identified lower insulin and C-peptide in the interrupted condition (P = 0.007 and P = 0.029, respectively); the intervention reduced insulin AUC by 21% (P < 0.001) and C-peptide AUC 18% (P = 0.001) and improved estimated insulin sensitivity (P = 0.013). Neither buffet total energy intake (1,262 ± 480 vs. 1,260 ± 475 kcal; P = 0.89) nor macronutrient composition of the meal (P values >0.38) differed between conditions significantly. CONCLUSIONS: Interrupting sitting with brief moderate-intensity walking improved glucose metabolism without significantly increasing energy intake in children with overweight or obesity. Interrupting sedentary behavior may be a promising intervention strategy for reducing metabolic risk in such children.

Effects of Interrupting Children's Sedentary Behaviors With Activity on Metabolic Function: A Randomized Trial.

CONTEXT: Limited data suggest that interrupting sedentary behaviors with activity improves metabolic parameters in adults. OBJECTIVE: We tested whether interrupting sitting with short, moderate-intensity walking bouts improved glucose tolerance in children. DESIGN: Participants underwent two experimental conditions in random order on different days: continuous sitting for 3 hours or sitting interrupted by walking (3 min of moderate-intensity walking every 30 min). Insulin, C-peptide, glucose, and free fatty acids were measured every 30 minutes for 3 hours during an oral glucose tolerance test. Area under the curve (AUC) was calculated from hormone and substrate measurements. Children were given a buffet meal after each condition. SETTING: The study was conducted at the National Institutes of Health Hatfield Clinical Research Center. PARTICIPANTS: Twenty-eight normal-weight 7-11 year olds participated. MAIN OUTCOMES: Patterns of substrate/hormone secretion and AUC, as well as energy intake, were examined by experimental condition. RESULTS: Interrupting sitting resulted in a 32% lower insulin AUC (P < .001), 17% lower C-peptide AUC (P < .001), and 7% lower glucose AUC (P = .018) vs continuous sitting. Mixed model results indicated that insulin (P = .036) and free fatty acid concentrations (P = .009) were significantly lower in the interrupted vs the continuous sitting condition. Lunchtime buffet meal energy intake did not significantly differ between the conditions (975 ± 387 vs 963 ± 309 kcal; P = .85). CONCLUSIONS: Interrupting sedentary time with brief moderate-intensity walking improved short-term metabolic function in non-overweight children without increasing subsequent energy intake. These findings suggest that interrupting sedentary behavior may be a promising prevention strategy for reducing cardiometabolic risk in children.