The purpose of this study is to assess the efficacy of a family-based digital (web and mobile phone-based) program known as Healthy Together ("Juntos") in preventing increases in body mass index and improving moderate-to-vigorous physical activity, diet quality, and percentage body fat among Hispanic adolescents.

Inclusion Criteria:

Adolescent

1. Lives with participating biological parent or legal guardian;
2. Self-identifies as Hispanic;
3. Is between the ages of 12-15years old;
4. Has access to a smartphone;
5. Does not meet recommendations for physical activity as determined by a validated 2-item screener;
6. Does not meet recommendations for daily fruit and vegetable intake (proxy for diet quality) as determined by a validated 2-item screener;
7. Exceeds recommendations for screen time (proxy for sedentary behavior) as determined by a validated 6-item screener

Parent

1. Is the biological parent or legal guardian of and lives with the adolescent;
2. Self-identifies as Hispanic;
3. Has access to a smartphone;

Exclusion Criteria:

Adolescent

1. Has BMI <5th (underweight) or ≥95th percentile (obesity);
2. Has a parent-reported chronic medical condition (e.g., type 2 diabetes) that requires more intensive intervention;
3. Has parent-reported responses on a physical activity readiness questionnaire (PAR-Q) that indicates a serious health issue, and a physician does not approve participation;
4. Has a parent-reported cognitive or developmental delay (e.g., Down Syndrome) that may interfere with understanding program materials.

Parent

1. Provides PAR-Q responses that indicate a serious health issue and a physician does not approve participation;
2. Reports family plans to move out of South Florida during the study follow-up period