Little is known about body composition in Parkinson's disease (PD). We studied 35 patients (20 male, 15 female subjects; mean age 69.7+/-5.8 years) with advanced PD by anthropometry, dual-energy X-ray absorptiometry (DEXA), and serum 25-OH vitamin D measurement. Over 70% of patients had a disease duration of more than 4 years; all were on L-dopa treatment. Low levels of serum 25-OH vitamin D were present in 41% of the patients. The mean body mass index (BMI) was 25.3+/-4.3 kg/m(2) (range 17.1-37.3). Mid-arm muscle circumference was below the 10th percentile in 23%. For whole-body mean (+/-SD) bone mineral density, the T score was below -1 SD in 35% of patients, and the Z score was below -1 SD in 24%. Percent fat mass measured with DEXA was 30.6+/-11.4% (range 10.1-45.5) in the overall sample; it was 21.1+/-8.8% (range 10.1-30.4) in male subjects and 38.1+/-9.2% (range 25.8-45.5) in female subjects. We conclude that advanced-stage PD may show excess adiposity coexisting with depletion of lean body mass (sarcopenic obesity), in addition to decreased whole-body bone mineral density associated with low serum 25-OH vitamin D. A low level of physical activity and inadequate exposure to sunlight are likely to be among the putative causes.