Body composition and fatness patterns in Prader-Willi syndrome: comparison with simple obesity.

OBJECTIVE: To characterize the body composition of Prader-Willi syndrome (PWS) subjects and compare with simple obesity.

RESEARCH METHODS AND PROCEDURES: Seventy-two individuals (27 PWS deletion, 21 PWS uniparental disomy, and 24 obese controls) 10 to 49 years old were studied with the use of DXA. Body composition measures were obtained, and regional fat and lean mass patterns were characterized. Significant differences were assessed with Student's t test and ANOVA adjusting for age, gender, and BMI.

RESULTS: Significant differences between the PWS and obese groups were found for lean measures of the arms, legs, and trunk. Total lean mass was significantly lower in PWS than in obese subjects for arms, trunk, and especially legs. Furthermore, two body regions (legs and trunk) showed significant differences for fat and lean measures between PWS and obese males. However, significant differences between PWS and obese females for these measures were found only for the legs. No significant differences were identified between PWS deletion and uniparental disomy subjects.

DISCUSSION: Our results demonstrate that PWS individuals do, in fact, have an unusual body composition and fatness patterns, characterized by reduced lean tissue and increased adiposity, with PWS males contributing most with fat patterns more similar to females.