THE ROLE OF GALLBLADDER EMPTYING IN GALLSTONE FORMATION DURING DIET-INDUCED RAPID WEIGHT-LOSS

Obese persons are at risk for cholesterol gallstones because their bil e is saturated with cholesterol, The risk increases during rapid weigh t loss by means of certain very-low calorie diets or gastric bypass su rgery. Gallstone risk factors during rapid weight loss include increas ed bile cholesterol saturation index and gallbladder stasis, Obese sub jects were randomized to one of two low calorie liquid diets for rapid weight loss: a 520-kcal diet with less than 2 g fat/d, and a 900-kcal diet with 30 g fat/d (including one 10-g fat meal to stimulate maxima l gallbladder emptying), Bile and blood lipids, saturation index, leuk ocyte 3-hydroxy-3-methylglutaryl coenzyme A (HMG CoA) reductase activi ty, and ultrasonographic gallbladder emptying were measured repeatedly during dietary treatment, Both diets produced comparable weight loss of 22%. Bile cholesterol saturation index increased during both diets (26%), but fell to 15% below prediet level after weight loss, Compared with subjects' maximal gallbladder emptying fraction of 66%, the 520- kcal diet provided poor gallbladder emptying (35%), whereas the 10-g fat meal of the 900-kcal diet provided maximal emptying, Gallstones de veloped in four of six 520-kcal subjects and none of seven 900-kcal su bjects (P = .021), an unanticipated difference that resulted in pre ma ture study termination for ethical reasons. Blood lipids and HMG CoA r eductase activity in mononuclear leukocytes fell at week 8 during both diets, but recovered while weight was still being lost, The findings suggest that gallstone risk during rapid weight loss may be reduced by maintenance of gallbladder emptying with a small amount of dietary fa t. Ultimately, weight loss reduced bile cholesterol saturation and imp roved high-density lipoprotein (HDL) levels.