Effects of interrupting daily sedentary behavior on children's glucose metabolism: A 6-day randomized controlled trial.

BACKGROUND: Metabolic disease risk in youth is influenced by sedentary behaviors. Acute in-lab studies show that, during a single day, interrupting a sedentary period with short bouts of physical activity improves glucometabolic outcomes. OBJECTIVE: To determine if acutely improved glucose metabolism persists after multi-day interruptions of sitting with walking brief bouts. We hypothesized that children who underwent interrupting sitting on multiple days would demonstrate lower insulin area under the curve during an oral glucose tolerance test compared to uninterrupted sitting. METHODS: Healthy, normoglycemic children (N = 109) ages 7-11 years were randomized to one of two conditions: Control (3 h of daily Uninterrupted Sitting) or Interrupted Sitting (3-min of moderate-intensity walking every 30 min for 3 h daily); with dietary intake controlled through provision of foodstuffs for the entire experiment. Participants attended six consecutive daily visits at a research ambulatory unit. The primary outcome was insulin area under the curve during the oral glucose tolerance test on day 6 during interrupted or uninterrupted sitting; secondary outcomes included glucose and c-peptide area under the curve, energy intake at a buffet meal on day 6, and free-living activity. RESULTS: Among 93 children (42 uninterrupted sitting, 51 interrupted sitting), daily interrupted sitting resulted in 21% lower insulin (ß = 0.102 CI:0.032-0.172, p = 0.005) and a 10% lower C-peptide (ß = 0.043, CI:0.001-0.084, p = 0.045) area under the curve. Matsuda and Glucose Effectiveness Indices were also improved (p's < 0.05). There were no group differences in energy intake or expenditure. CONCLUSIONS: Sustained behavioral change by interrupting sedentary behaviors is a promising intervention strategy for improving metabolic risk in children.

Associations between weight-based teasing and disordered eating behaviors among youth.

Weight-based teasing (WBT) is commonly reported among youth and is associated with disinhibited and disordered eating. Specifically, youth who experience WBT may engage in disordered eating behaviors to cope with the resultant negative affect. Therefore, we examined associations between WBT and disordered eating behaviors among youth and assessed whether negative affect mediated these relationships. Two hundred one non-treatment seeking youth (8-17y) completed questionnaires assessing WBT, disinhibited eating, depression, and anxiety. Disordered eating and loss-of-control (LOC) eating were assessed via semi-structured interview. Analyses of covariance were conducted to examine relationships between WBT and eating-related variables, and bootstrapping mediation models were used to evaluate negative affect (a composite of depressive and anxiety symptoms) as a mediator of these associations. All models were adjusted for sex, race, age, and adiposity. Among 201 participants (13.1 ± 2.8y; 54.2% female; 30.3% Black; 32.8% with overweight/obesity), WBT was associated with emotional eating, eating in the absence of hunger, and disordered eating attitudes and behaviors (ps ≤ 0.02). These associations were all mediated by negative affect. WBT was also associated with a threefold greater likelihood of reporting a recent LOC eating episode (p = .049). Among boys and girls across weight strata, WBT was associated with multiple aspects of disordered eating and these relationships were mediated by negative affect. Longitudinal studies are needed to clarify the directionality of these associations and to identify subgroups of youth that may be particularly vulnerable to WBT and its sequelae.

Estimating plasma glucose with the FreeStyle Libre Pro continuous glucose monitor during oral glucose tolerance tests in youth without diabetes.

Few studies have assessed the accuracy of the FreeStyle Libre Pro (FLP) continuous glucose monitor for estimating plasma glucose (PG) in non-diabetic children. OBJECTIVE: Determine the accuracy of FLP compared to PG during OGTT in healthy children. SUBJECTS: Children (7-11.99 years) with healthy weight and overweight/obesity (n = 33; 52% male). METHODS: Participants wore the FLP before and during a 2-hour OGTT; PG was measured at 30 minutes intervals. Potential systematic- and magnitude-related biases for FLP vs PG were examined. RESULTS: FLP 15-minute averages and PG were correlated at most timepoints during OGTT (r2 = 0.35-0.69, P's < .001 for time point 30-120 minutes) and for PG area under the curve (AUC) (r2 = 0.65, P < .0001). There were no systematic biases as assessed by Bland-Altman analyses for FLP AUC or for FLP at each OGTT timepoint. However, for fasting glucose, a significant magnitude bias was noted (r2 = 0.38, P < .001), such that lower PG was underestimated, and higher PG was overestimated by FLP readings; further, there was poor correlation between fasting PG and FLP (r2 = 0.06, P = .22). BMIz was also associated with FLP accuracy: FLP overestimated PG in children with low BMIz and underestimated PG in those with overweight/obesity for OGTT AUC and OGTT PG at baseline, 60, and 120 minutes (all P's ≤ .015). No adverse events occurred with FLP. CONCLUSIONS: Among children without diabetes, the FLP was well tolerated and correlated with post-OGTT glucose, but had magnitude bias affecting fasting glucose and appeared to underestimate plasma glucose in those with overweight/obesity. These results suggest potential limitations for the utility of the FLP for research.

Associations of Weekday and Weekend Sleep with Children's Reported Eating in the Absence of Hunger.

Insufficient average sleep duration has been inconsistently associated with poor diet and obesity risks in youth. Inconsistencies in findings across studies may be due to a general failure to examine associations in weekday versus weekend sleep. We hypothesized that greater variations in weekday and weekend sleep duration would be associated with more disinhibited eating behaviors, which, in turn, might be involved in the relationship between sleep and weight. We, therefore, examined, among healthy, non-treatment seeking youth, the associations of average weekly, weekend, and weekday sleep duration with eating in the absence of hunger (EAH), a disinhibited eating behavior associated with disordered eating and obesity. Sleep was assessed via actigraphy for 14 days. Participants completed a self-report measure of EAH. Adiposity was measured by dual-energy X-ray absorptiometry. Linear regressions were used to test the associations of sleep duration with EAH and the associations of sleep duration and EAH, with fat mass. Among 123 participants (8-17 years, 52.0% female, and 30.9% with overweight), there was no significant association between average weekly sleep and EAH. Further, there was no significant association among average weekly sleep duration or EAH and fat mass. However, average weekday sleep was negatively associated, and average weekend sleep was positively associated, with EAH (ps < 0.02). Weekend "catch-up" sleep (the difference between weekend and weekday sleep) was positively associated with EAH (p < 0.01). Findings indicate that shorter weekday sleep and greater weekend "catch-up" sleep are associated with EAH, which may place youth at risk for the development of excess weight gain over time.

Free Fatty Acids as an Indicator of the Nonfasted State in Children.

BACKGROUND: Ensuring children are fasting for blood draws is necessary to diagnose abnormalities in glucose homeostasis. We sought to determine if serum free fatty acid (FFA) concentrations might be a useful marker to differentiate the fed and fasted states among children. METHODS: A total of 442 inpatient (fasting) and 323 (postglucose load) oral glucose tolerance test samples of glucose, insulin, and FFA from children (age 5-18 years) who had healthy weight, overweight, or obesity were examined by receiver operating characteristic (ROC) curve analysis to identify a cut point for nonfasting. In a cross-sectional study, we compared mean FFA and percentage of FFA values below this cut point as a function of inpatient (n = 442) versus outpatient (n = 442) setting. RESULTS: The area under the curve of FFA was significantly better (P values < .001) than the area under the curve of glucose or insulin for identifying nonfasting. FFA <287 mEq/mL had 99.0% sensitivity and 98.0% specificity for nonfasting. Mean FFA was lower in outpatients than inpatients (P < .001); only 1.6% inpatient but 9.7% outpatient FFA values were consistent with nonfasting (P < .001). CONCLUSIONS: Clinicians cannot assume that pediatric patients are adequately fasted on arrival for fasting blood work. On the basis of having significantly lower outpatient than inpatient FFA values and more frequently suppressed FFA, children appeared less likely to be fasting at outpatient appointments. FFA value <287 mEq/mL was a sensitive and specific cutoff for nonfasting in children that may prove clinically useful.

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.