Dietary intake of protein is positively associated with percent body fat in middle-aged and older adults.

Data on associations between dietary intake of macronutrients and body composition in the general population are sparse. This population-based, cross-sectional study of 4478 middle-aged (47-49 y) and elderly (71-74 y) men and women from the Hordaland Health Study in western Norway was conducted using a validated FFQ and measurements by dual-energy X-ray absorptiometry. The relation between macronutrient intake [percentage of total energy intake (E%)] and percent body fat was investigated in the total population and in a subgroup with intermediate BMI and stable weight (BMI within the 25th-75th percentile and weight change <5% during the last 6 y; n = 975). In the total population, protein intake (E%) was associated with higher percent body fat (partial r = 0.11; P < 0.001) in multivariate linear regression analysis. In the subgroup with intermediate BMI and stable weight, there was no association between protein intake (E%) and percent body fat. Fat intake (E%) was positively associated (partial r = 0.07) whereas carbohydrate intake (E%) was inversely associated (partial r = -0.07) with percent body fat (P = 0.042 for both) in the subgroup with intermediate BMI and stable weight. Both in the total population and in the stable weight group, physical activity was inversely related to adiposity (partial r = -0.15 and -0.12, respectively; P < 0.001). Our results may explain some of the conflicting data on the effects of macronutrients in different populations and suggest the potential importance of protein intake as a factor in obesity.