Relationships of physical activity with dietary behaviors among adults

Background. Physical activity and diet are important influences on health, but few data are available about the relationship between these two factors. The purpose of this study was to examine relationships between physical activity and dietary quality and to identify determinants of the combination of sedentary behavior and suboptimal diet. Methods. The design of this study was cross-sectional. The setting was a large managed-care organization and the participants were 1,322 racially diverse men and women ages 25-91 years. We categorized subjects' physical activity into vigorous, moderate, and sedentary based on answers to two validated interviewer-administered questions about intensity and duration of specified activities. Dietary assessment was by means of a validated short food frequency questionnaire. We defined suboptimal diet as consuming unhealthful quantities of at least two of the following five food groups: fruits, vegetables, whole grain foods, whole-fat dairy foods, and red and processed meats. Results. Seven hundred fifty-four (57%) subjects were sedentary and 617 (47%) consumed a suboptimal diet. Using multiple linear regression, we found that sedentary individuals consumed smaller amounts of foods and nutrients considered to be healthful, such as fruits and vegetables, fiber, calcium, folate, and vitamins A, C, and E, than more active participants. For nutrients considered to be harmful, such as saturated fat, trans fat, and dietary cholesterol, the association with physical activity was inverse. In multiple logistic regression analyses, the strongest sociodemographic correlates of the joint presence of inactivity and poor diet were less education [odds ratio for 1-year decrease 1.14 (95% confidence interval 1.06, 1.22)], nonwhite race [1.48 (1.05, 2.07)], and nonmarried status [1.49 (1.06, 2.10)]. Conclusions. Physical activity and diet quality are correlated behaviors. Suboptimal diet and sedentary behavior tend to cluster in individuals who are less educated, not married, and of nonwhite race. Programs that target diet and activity together, informed by their joint determinants, may attain enhanced outcomes. (C) 2001 American Health Foundation and Academic Press.