Circuit Training and Motivational Interviewing to Reduce Type 2 Diabetes in Youth

The overall goal of this project is to examine the physiological and metabolic effects of a 16-week circuit-training (strength training + aerobic activities) program, with and without a behavioral component utilizing motivational interviewing, in 45 overweight Latina adolescent girls (14-18 years of age). This 16-week randomized control study will examine the incremental effects of the following 3 intervention groups on insulin sensitivity, insulin secretion, adiposity, and habitual and ad libitum physical activity: * Control group (delayed circuit training intervention; n=15) * Circuit training group (strength + aerobic training; 2 times per week; n=15) * Circuit training (same as above) + weekly motivational interviewing sessions (n=15) Specific Aim 1: To examine the effects of a 16-week circuit training program on adiposity, insulin dynamics, other associated hormones and adipocytokines, cardiorespiratory fitness, and muscular strength in overweight Latina adolescent girls. Hypothesis 1: Participation in the circuit-training program will result in significant improvements in both physiological and metabolic outcomes, including: a) body composition as measured by DEXA, b) fat distribution as measured by MRI, c) adipose tissue hormones (e.g. leptin, adiponectin, TNF-α) as measured by fasting blood samples, d) insulin sensitivity and secretion as measured by frequently sampled intravenous tolerance test, e) aerobic fitness as measured by the single stage submaximal treadmill test, and f) increase muscular strength as measured by repetition maximums. Specific Aim 2: To examine the incremental effects of adding the motivational interviewing sessions to the circuit training on self-selected ad libitum physical activity during a 5-hour observational period, habitual physical activity levels using 7 day accelerometry, and the meanings and motivation to exercise using questionnaires before and after the intervention. Hypothesis 2: The addition of motivational interview