Do changes in physical activity lead to dietary changes in middle and old age?

Research examining the relationship between dietary factors and physical activity patterns has yielded conflicting findings. Few prospective studies have examined whether individuals who change their level of physical activity make corresponding changes in their diet.

The current study examined, in two randomized clinical trials of physical activity, whether self-report of dietary factors changed over a 1-year period, whether these changes differed by gender or exercise-intervention group, and whether changes in physical activity led to changes in dietary factors. Participants included 268 men and women aged 50-65 years who participated in the Stanford-Sunnyvale Health Improvement Project I (SSHIP-I) and 103 men and women aged 65-82 years who participated in SSHIP-II. In both trials we recruited participants through random-digit telephone dialing and citywide promotion.

Overall, participants adopted healthier diets over the 1-year period. The SSHIP-I participants decreased their consumption of total calories, total fat, saturated fat, protein, and cholesterol. The SSHIP-II participants decreased their consumption of high-fat, high-cholesterol foods. The SSHIP-I women were more likely than men to decrease their intake of total fat and protein (p < 0.01), as well as total calories, saturated fat, and cholesterol (p < 0.05). However, we found that changes in physical activity were not associated with changes in self-report measures of dietary habits.

We found no evidence to support the idea that changes in physical activity are a gateway for changes in dietary factors in middle-aged and older adults.