Effects of Multi-day Interruptions in Sitting on Type 2 Diabetes-relevant Outcomes in Children

Rationale: Sedentary behavior (SB) contributes to increased risk for obesity and metabolic disease, cognitive deficits, affect disorders, and cardiovascular disease over the lifespan. These are critical outcomes because children with these risk factors are more likely to develop type 2 diabetes mellitus (T2DM). SB increases T2DM risk by promoting hyperglycemia and greater postprandial glycemic variability as well as via cognitive detriments and depressive symptoms that lead to poor energy balance behaviors, obesity, and worsening insulin resistance. Additionally, prolonged SB may contribute to dominance of the sympathetic nervous system and lead to poor cardiovascular disease outcomes. Physical activity can reduce these risk factors, however less than half of US youth meet guideline recommendations, and physical activity continues to decline throughout adolescence. Thus, there is a critical need to test alternative intervention approaches to sustained bouts of exercise for the prevention of T2DM in children. The investigators were the first to show that interrupting SB with short, 3-minute, bouts of moderate exercise improved glucose tolerance and negative mood in a single 3-hour session. However, it is unknown whether these short-term improvements translate to sustained multi-day benefits to metabolic, cognitive, mood, and cardiac autonomic nervous system outcomes.

Intervention: This phase II randomized controlled trial (RCT) will compare the effects of SB interruptions vs. sustained bouts of exercise to prolonged sitting in 8-11-year-old children with overweight/obesity. Participants (N=150 (50 per group)) will be recruited from the community. The participants will wear continuous glucose monitors for one week and complete pre- and post- experiment 3-hour oral glucose tolerance tests (OGTT). Children will be randomized to 7 consecutive days of one of the following 3-hour experimental conditions: a) continuous sitting (SIT); b) sitting interrupted by 3-minute bouts of moderate-intensity walking every 30 minutes (SIT+WALK); or c) a single 18-minute bout of moderate-intensity walking followed by continuous sitting (EX).

Objectives/Purpose: The overall goal of this study is to test the efficacy of multi-day effects of interrupting SB as a T2DM prevention strategy in youth with overweight/obesity. This proposal will address the following aims: (1) determine the multi-day efficacy of interrupting sitting on glucose homeostasis measured by continuous glucose monitor and oral glucose tolerance tests; (2) determine the multi-day efficacy of interrupting sitting on cognitive function improvements; (3) determine the multi-day efficacy of interrupting sitting on affect and anxiety improvements; and (4) determine the multi-day efficacy of interrupting sitting on cardiac autonomic nervous system improvements measured by heart rate variability.

Study Population: The study population will consist of children with overweight/obesity recruited from the greater Los Angeles area. Children will be screened for eligibility (no evidence of type 2 diabetes, have overweight/obesity, be in good health, and be in early pubertal stages).

Study Methodology: This study is a phase II RCT with 3 study arms. Participants (N=150) will complete one screening visit to determine eligibility, complete a fitness test, and body composition analysis via dual x-ray absorptiometry (DEXA). All participants will complete two 3-hour in-lab oral glucose tolerance tests (spaced 6 days apart). Participants will wear an activity monitor on the right thigh and an electrocardiogram (ECG) monitor on the chest 7 days to determine baseline activity levels and heart rate variability, respectively. Then, participants will complete 7 consecutive in-lab sessions (SIT, SIT+WALK, or EX), with a 3-hour OGTT on Days 1 and 7. Participants will wear activity monitors, continuous glucose monitors, and ECG monitors during these 7 days of experimental sessions. Questionnaires will assess dietary intake, affect, anxiety, and mood, and the NIH Toolbox will assess executive cognitive function.

Study Arms: Participants will be randomized to 7 consecutive days of one of the following 3-hour experimental conditions in the lab: a) continuous sitting (SIT); b) sitting interrupted by 3-minute bouts of moderate-intensity walking every 30 minutes (SIT+WALK); or c) a single 18-minute bout of moderate-intensity walking followed by continuous sitting (EX).

Endpoints/Outcomes: The primary endpoints are: insulin, C-peptide, and glucose area under the curve (AUC) in the in-lab experiments, and glucose AUC from the continuous glucose monitor. Secondary endpoints are positive and negative affect, anxiety, executive cognitive function, and heart rate variability metrics.

Follow-up: Study duration is estimated as 14 days minimum and 30 days maximum, to allow for a 7-21 day period between the screening and experimental visits.

Statistical Analyses: The populations for analyses include the full analytical dataset which consists of all randomized study participants; the investigators will employ per protocol and intent to treat analyses.