Just-in-time Adaptive Intervention Messaging in a Digital Weight Loss Intervention for Young Adults

Inclusion Criteria: * Body mass index (BMI) of 25 - 45 kg/m\^2 at baseline * English-speaking, reading, and writing * Own a smartphone with a data and text messaging plan Exclusion Criteria: * Type 1 diabetes or currently receiving medical treatment for Type 2 diabetes * Report a heart condition, chest pain during periods of activity or rest, or loss of consciousness on the Physical Activity Readiness Questionnaire (PAR-Q; items 1-4). * Other health problems which may influence the ability to walk for physical activity or be associated with unintentional weight change, including cancer treatment within the past 5 years or tuberculosis * Lost 10 lbs. or more of body weight (and kept it off) in the last 6 months * Past diagnosis of or receiving treatment for a clinically diagnosed eating disorder (anorexia nervosa or bulimia nervosa) * Current symptoms of alcohol or substance dependence * Currently pregnant, pregnant within the past 6 months, or planning to become pregnant within the next 6 months * Untreated thyroid disease or any changes (type or dose) in thyroid medication in last 6 months * Hospitalization for depression or other psychiatric disorder within the past 12 months * History of psychotic disorder or bipolar disorder * Currently participating in a weight loss, nutrition, or physical activity study or program or other study that would interfere with this study * Currently using prescription medications with known effects on appetite or weight (e.g., oral steroid…