Inclusion Criteria:  1) Males or females age 13 to 22 years. 2) Overweight or obese (BMI ≥85th percentile for age/sex, or ≥25 kg/m2 for participants ≥18 years) 3) Diagnosis with prediabetes or type 2 diabetes 4) Consent (subjects 18 and older), Parental/guardian permission (subjects 13-17), assent (subjects 13-17) 5) Willingness to wear Fitbit during waking hours daily for duration of run-in and intervention. 6) Possession of a smartphone.  Exclusion Criteria:  1) Potential subject unable to speak or read in English 2) Severe cognitive impairment 3) Permanent or temporary physical disability that impairs ambulation or precludes engagement in MVPA 4) Current pregnancy 5) Previously-diagnosed or current restrictive or purging eating disorder 6) Moderate to vigorous physical activity (MVPA) >30 minutes per day or Fitbit wear < 4 days during second week of 2-week run-in period