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

The purpose of this micro-randomized trial is to evaluate the effects of 7 types of intervention messages targeting specific behavior change techniques (i.e., BCT messages) delivered in "just-in-time" (JIT) moments on daily achievement of weight-related behavioral goals among n=201 young adults with overweight and obesity, participating in a digital, mobile comprehensive lifestyle intervention. "Just-in-time adaptive interventions" (JITAIs) are an alternative to the "one size fits all" approach of mobile intervention development that can provide tailored, real-time messaging and support for young adults.

Inclusion Criteria:Body mass index (BMI) of 25 - 45 kg/m^2 at baselineEnglish-speaking, reading, and writingOwn a smartphone with a data and text messaging planAchieve fewer than 210 minutes/week of moderate to vigorous intensity physical activity at baselineExclusion Criteria:Type 1 diabetes or currently receiving medical treatment for Type 2 diabetesReport 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 tuberculosisLost 10 lbs. or more of body weight (and kept it off) in the last 3 monthsPast diagnosis of or receiving treatment for a clinically diagnosed eating disorder (anorexia nervosa or bulimia nervosa) or any compensatory behaviors within the previous 3 monthsCurrent symptoms of alcohol or substance dependenceCurrently pregnant, pregnant within the past 6 months, or planning to become pregnant within the next 6 monthsUntreated thyroid disease or any changes (type or dose) in thyroid medication in last 6 monthsHospitalization for depression or other psychiatric disorder within the past 12 monthsHistory of psychotic disorder or bipolar disorderCurrently participating in a weight loss, nutrition, or physical activity study or program or other study that would interfere with this studyCurrently using prescription medications with known effects on appetite or weight (e.g., oral steroids, weight loss medications), with the exception of individuals on a stable dose of Selective Serotonin Reuptake Inhibitors (SSRIs) for 3 months)Previous surgical procedure for weight loss or planned weight loss surgery in the next yearAnother member of the household is a participant or staff member on this trialReason to suspect that the participant would not adhere to the study interventionReside outside of the United States