Inclusion Criteria:

• Overweight (age- & sex-specific body mass index ≥ 85th percentile based on CDC BMI growth charts [US Department of Health and Human Services, 2000], calculated by Epi Info Software, version 3.3)
• Latino (both sets of grandparents must be of Latino heritage as defined by self-report; limited to Latinos to maintain a homogeneous sample and because Latinos are at increased risk of insulin resistance and type 2 diabetes.) If the participant or the parent is unsure of the country of origin of all 4 grandparents they will be excluded from the study. The participants and their families are not asked whether or not their grandparents are undocumented immigrants.

Exclusion Criteria:

• Presently taking medication(s) or diagnosed with any syndrome or disease that could influence dietary intake, exercise ability, body composition and fat distribution, or insulin action and secretion.
• Previously diagnosed with any major illness since birth (e.g. severe intrauterine growth retardation, chronic birth asphyxia, cancer).
• Children will not be eligible for participation if they have any diagnostic criteria for diabetes including polyuria, polydipsia with or without unexplained weight loss, fasting plasma glucose > 126 mg/dl, or a 2-hour plasma glucose >200 mg/dL during an oral glucose tolerance test. Children will also be excluded if they test positive for diabetes-related auto-antibodies, including ICA512 and GAD. Children testing positive for type 2 diabetes will be referred for treatment. Children with impaired glucose tolerance (fasting glucose >110 mg/dL or 2-hour glucose >140 mg/dl during an OGTT) and/or conditions associated with insulin resistance (e.g. acanthosis nigricans, hypertension, dyslipidemia, PCOS) will be eligible, as long as they are not receiving treatment and meet other eligibility criteria.
• Participants who are involved in any weight training, exercise, nutrition, or weight loss program or have been in the past 6 months.
• Participants that do not follow the rules and guidelines of appropriate conduct during participation, i.e., disruptive behavior, derogatory or racist comments, or any acts of physical violence towards study staff or other participants, and use of illegal substances. The principal investigator Dr. Michael Goran will decide if this conduct warrants exclusion or removal from the study.
• Pregnancy test comes out positive.
• Children who live further than 20 miles away from the General Clinic Research Center (GCRC).
• We can terminate participation if the child fails to follow the rules and guidelines of appropriate behavior and conduct during participation.