Background: Few studies have evaluated how to combine dietary and physical activity (PA) interventions to enhance adherence.
Purpose: We tested how sequential versus simultaneous diet plus PA interventions affected behavior changes.
Methods: Two hundred participants over age 44 years not meeting national PA and dietary recommendations (daily fruit and vegetable servings and percent of calories from saturated fat) were randomized to one of four 12-month telephone interventions: sequential (exercise first or diet first), simultaneous, or attention control. At 4 months, the other health behavior was added in the sequential arms.
Results: Ninety-three percent of participants were retained through 12 months. At 4 months, only exercise first improved PA, and only the simultaneous and diet-first interventions improved dietary variables. At 12 months, mean levels of all behaviors in the simultaneous arm met recommendations, though not in the exercise- and diet-first arms.
Conclusions: We observed a possible behavioral suppression effect of early dietary intervention on PA that merits investigation.
Trial registration: ClinicalTrials.gov NCT00131105.