OBJECTIVE: To investigate if dietary protein and degree of adiposity interacts in relation to change in body weight and waist circumference (WC) in the general population.

METHODS: In total 22,433 middle-aged individuals with dietary assessment at baseline and anthropometry at baseline and at follow-up about 5 years later were analyzed with multiple linear regression and dietary macronutrient substitution models. Interactions between dietary protein and baseline body mass index (BMI) and baseline WC adjusted for BMI (WCBMI ) (divided in tertiles; nine groups total), were analyzed in relation to changes in body weight (BW) and changes WC adjusted for change in BW.

RESULTS: Baseline intake of protein was not significantly associated with changes in weight or waist circumference. Across the nine groups of baseline BMI and WCBMI there were no distinct trends in the associations between dietary protein, whether replacing carbohydrate or fat, and weight change. However, individuals in the highest tertile of baseline BMI (irrespective of baseline WCBMI ) had significantly inverse change in waist circumference when protein replaced carbohydrate, but not when protein replaced fat.

CONCLUSION: Replacing carbohydrate with protein in the diet may prevent a relative increase in WC in individuals with a greater BMI.