BACKGROUND:~The majority of adult Americans consume a high saturated fat diet, have a low fruit and vegetable (F/V) intake, and lead a sedentary lifestyle. This unhealthy lifestyle heightens their risk for cardiovascular disease and cancer. Improving diet and activity can reduce risk, but the best prescription to promote a healthier diet and a more active lifestyle remains unknown. This study will randomly assign participants to 4 groups, which will include all combinations of increasing healthy eating and activity and decreasing unhealthy eating and activity. The Familiarity Hypothesis predicts that the most familiar dieting prescription (decrease fat, increase physical activity) will maximize healthy behavior change. The Optimal Substitution Hypothesis, based on Behavioral Economic Theory, predicts that increasing F/V intake while decreasing sedentary behavior will surpass alternative methods by maximizing behavioral substitution of healthful eating and activity for unhealthful eating and activity. The Low Inhibitory Demand Hypothesis, based on Self-Control Theory, predicts that increasing F/Vs while increasing physical activity will be most successful because this prescription places the fewest demands on self-control resources.~DESIGN NARRATIVE:~The study will randomize 200 sedentary community-dwelling adults with a suboptimal diet to 1 of 4 groups including: 1) increase healthy eating and activity; 2) decrease unhealthy eating and activity; 3) increase healthy eating and decrease unhealthy activity; and 4) decrease unhealthy eating and increase healthy physical activity. Subjects will self-monitor diet, physical activity, and mood via PDAs during a 2-week baseline period, a 3-week prescription period (when payment is contingent upon changing eating and activity simultaneously to targeted standards), and a 4-month maintenance period. Targeted and collateral diet and activity changes will be measured by self report, accelerometer, and grocery receipts. Bogus pipeline urinary testing will encourage adherence. Laboratory testing will measure behavioral choices, craving, and attentional allocation to restricted foods and activities in a permissive context in order to shed light on behavioral and psychological processes that mediate healthy lifestyle change. Findings will help to fill an important gap in clinical knowledge about how to optimize healthy simultaneous change in diet and activity among adults.
The purpose of this study is to examine the impact of diet and exercise on an individual's health.