A randomized trial of sequential and simultaneous multiple behavior change interventions for physical activity and fat intake.

Background: Major questions remain unanswered about how best to accomplish multiple behavior change. The purpose of this study was to evaluate whether there are differences in successfully changing multiple behaviors in computer-tailored sequential and simultaneous interventions for physical activity (PA) promotion and fat intake (FI) reduction.

Methods: Participants (N=567) were randomly assigned to receive an intervention for PA and FI simultaneously; PA at baseline and FI at 3 months; or FI at baseline and PA at 3 months. Successful behavior change at 6 months was defined as: >60 min PA increase and/or 5% FI reduction. Using multinomial logistic regression the odds ratios of successful behaviors change (none, PA only, FI only, or both) were determined for intervention mode, gender, age, BMI and education.

Results: Overall drop-out was 26%. There was no behavior change for 20.2% of participants; 30.5% successfully decreased FI; 15.8% successfully increased PA; 33.5% successfully changed both behaviors. Intervention mode, gender and age were not associated with successful behavior change. Compared to those that did not change any behaviors: participants that successfully changed FI were more likely to be overweight/obese (OR=1.85); and participants that successfully changed both behaviors were more likely to be overweight/obese (OR=2.13) and have lower education (OR=2.46).

Conclusions: Success in changing multiple behaviors was not associated with intervention mode; both simultaneous and sequential interventions can be applied. Being overweight might be an extra motivator to change health behaviors.