Biliary lipid composition in obesity.

Fasting gallbladder bile was obtained under standardized conditions from 15 gallstone-free obese subjects (greater than 130% of ideal weight) and 23 healthy control subjects matched for age, sex, and serum lipid levels. The proportion of cholesterol, expressed as molar percentage of total biliary lipids, was increased in obesity (10.8 +/- 0.6 versus 6.8 +/- 0.4 M % (mean +/- S.E.M.), P less than 0.001), whereas that of bile acids was decreased (64.7 +/- 1.3 versus 71.0 +/- 1.0 M %, P less than 0.001). The cholesterol saturation of bile was higher in obesity (141 +/- 7%) than in controls (96 +/- 5%, P less than 0.001). The results provide an explanation of the enhanced frequency of cholesterol gallstones in obese subjects.