Activity, Adiposity, and Appetite in Adolescents 2 Intervention

he objective of the study is to quantify the relationship between physical activity, metabolic function, and appetite in adolescents. To do this we will test our working hypothesis that high levels of regular moderate-to-vigorous physical activity (MVPA), as opposed to body weight status, results in a metabolic phenotype consisting of enhanced metabolic function and proper regulation of appetite. We will randomly assigning sedentary overweight/obese adolescents (N=44) to either a control or structured-exercise group for three months.

Our study statistician Dr. Vincent Staggs will randomize participants after final eligibility is determined to either the newsletter control or exercise intervention, balanced by gender to ensure equal composition of males and females.

The sample size for Study 2 (Aim 2) was calculated based on data from our lab; a small pilot study with sedentary and active periods to test the feasibility of our laboratory protocols. Based on this preliminary data, which is similar to data in the existing literature, we estimate changes in appetite ratings (hunger) 11% from baseline, equating to effect sizes of 0.67, resulting in sample size calculations of N=35. Assuming a drop-out rate of 10% (n=4) during the three month intervention, which is typically observed in similar interventions conducted by Mentor Dr. Donnelly, final sample size is set at N=40.

Data analysis will be completed by the PI with assistance from the statistician Dr. Staggs and the mentorship team. For visual analog scale (VAS) appetite measures, which are assessed at multiple time points within a single measurement session, we will conduct analyses in two ways. First, we will conduct between group analyses using each of the seven individual assessments (e.g. 60 min post-meal) to see if the values differ by physical activity or body weight group. Second, we will also calculate area under the curve (AUC) for each variable of interest (e.g. hunger, ghrelin), and use that measure for the test of group differences. To address Aim 1, hypothesis 2, we will repeat the analyses described above and include insulin sensitivity as a covariate. To address Aim 2, hypothesis 3, we will conduct between group analyses of change over time using repeated measures ANOVA, using the same analysis techniques for the appetite variables as described in Aim 1 (single assessment and AUC), with insulin sensitivity included as a covariate.

Appetite is considered the primary outcome of Aim 1 and 2. Subjective assessment of hunger and palatability will be completed using self-rated visual analogue scales (VAS), with each scale consisting of a 10-cm long line separating statements such as ?not at all hungry? and ?extremely hungry?. Perceptions of dietary restraint, disinhibition, and hunger will be measured during each measurement session prior to the fixed meal using the Three Factor Eating Questionnaire (TFEQ). The Control of Eating Questionnaire (CEQ) will be used to assess hunger, fullness, cravings, the desire to eat certain types of foods, and the ability to resist urges to eat. Objective assessment of appetite will be completed using blood samples taken from an indwelling catheter, and analyzed for episodic regulation of the following fasting and satiety hormones: glucose, insulin, leptin, ghrelin, glucagon-like peptide 1 (GLP-1), and peptide YY (PYY). All samples will be mixed a standard preservative (400 ?L of 10,000 KIU aprotinin), centrifuged, the plasma divided into aliquots and stored in -80?C freezer until analysis using standard kits at an outside certified clinical laboratory.