Do protein and energy intakes explain long-term changes in body composition?

Despite evidence that profiles of protein and energy intake can determine short-term (< 1 y) change in both lean and fat compartments,the role of diet in longer-term, age-related changes in body composition remains unclear.

This paper tests for long-term counterparts to the well-established short-term relationships between protein and energy intake and changes in body composition.

Using longitudinal data on 608 healthy, non-obese Chinese (50-69 y)from the 1993 and 1997 China Health and Nutrition Surveys, sex-specific regression models were created to determine if 3-day mean protein (%of energy) and energy (kJ) intakes at baseline predicted change in mid arm muscle area (MAMA) and waist circumference (WC).

Although sex-specific U-shaped associations were observed,higher energy intakes were associated with greater gain in WC and less loss of MAMA, and higher protein intakes with less loss of MAMA than lower intakes for both sexes, adjusting for baseline age, height, weight, MAMA, WC, smoking status, activity level, income and urban residence. For males, energy intake be low 95%of the Chinese RDA was associated with significantly smaller gains in WC and greater loss of MAMA than energy intake between 95-125% RDA. For both sexes, protein intake be low 10.4% of energy was associated with significantly greater loss of MAMA than intake between 10.4-12.1% of energy. For females, energy intake above 125% RDA was associated with significantly greater gains in body fat than intake between 95-125% RDA.

The results suggest that diet may play an important role in age-related change in body composition.