Physical activity planning interventions, body fat and energy-dense food intake in dyads: ripple, spillover, or compensatory effects?

ObjectivesIt is unclear if planning to change one behavior may prompt changes in other health behaviors or health outcomes. This study tested if physical activity (PA) planning interventions may result in (i) a body fat reduction in target persons and their dyadic partners (a ripple effect), (ii) a decrease in energy-dense food intake (a spillover effect), or an increase in energy-dense food intake (a compensatory effect).MethodN = 320 adult-adult dyads were assigned to an individual ('I-for-me'), dyadic ('we-for-me'), or collaborative ('we-for-us') PA planning intervention or a control condition. Body fat and energy-dense food intake were measured at baseline and at the 36-week follow-up.ResultsNo Time x Condition effects were found for target persons' body fat. There was a reduction in body fat among partners participating in any PA planning intervention, compared to the control condition. Across conditions, target persons and partners reduced energy-dense food intake over time. The reduction was smaller among target persons assigned to the individual PA planning condition compared to the control condition.ConclusionsPA planning interventions delivered to dyads may result in a ripple effect involving body fat reduction among partners. Among target persons, the individual PA planning may activate compensatory changes in energy-dense food intake.