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 interviewing will encourage and empower participants to be more active outside of the intervention and foster healthy physical activity behaviors in daily life. Improvements in physical activity behaviors will lead to greater improvements in all other health outcomes listed in specific aim 1 compared to circuit training alone and control group.

Inclusion Criteria:

• At Risk of Overweight and Overweight (age- & sex-specific body mass index ≥ 85th percentile based on CDC BMI growth charts [US Department of Health and Human Services, 2000]. There will not be an upper BMI limit. In our experience, we have had numerous children above the 99th percentile for BMI complete the outcome measures, and this group could benefit greatly from participation.
• Gender & Age: Females from grades 9th to 12th (approximately 14-18 years of age). We chose to study adolescents because pubertal youth will likely possess the requisite hormonal milieu needed to elicit physiologically and metabolic changes in response to resistance and aerobic training. In addition physical activity declines are more pronounced in minority females. By limiting the study to just females, we will retain a more homogenous group. This will eliminate sensitive gender issues related to exercise such as body image concerns, goal setting, and motivations for behavioral changes. To reduce effects of the menstrual cycle, all females will be tested during the follicular phase, while those with irregular/unpredictable menses will be studied at random times.
• Latino origin all four grandparents must be of Hispanic heritage (reported on screening forms). This approach is consistent with all of our previous and ongoing work.

Exclusion Criteria:

• Presently taking medication(s) or diagnosed with any syndrome or disease that could influence physical activity, body composition and fat distribution, or insulin action.
• Previously diagnosed with any major illness since birth (e.g. chronic birth asphyxia, cancer, etc.).
• Children with type 1 and/or type 2 diabetes will be excluded and referred to a physician. Children with impaired glucose tolerance (fasting glucose >100 mg/dL during a fasting blood draw) and/or conditions associated with insulin resistance (e.g. acanthosis nigricans, hypertension, dyslipidemia) will be eligible, as long as they are not receiving treatment and meet other eligibility criteria.
• Children who have any physical, cognitive, or psychological disabilities that would prevent them from participating in an exercise program.
• Currently, or in the past 6 months, involved with any dietary, physical activity or weight loss program.
• Children who live farther than 20 miles away from the GCRC.