Similarity in gallstone formation from 900 kcal/day diets containing 16 g vs 30 g of daily fat: evidence that fat restriction is not the main culprit of cholelithiasis during rapid weight reduction.

Diets containing essentially no fat, 1-2 g fat per day, have resulted in cholesterol gallstones. Greater fat may result in less gallbladder stasis. Do gallstones form with greater fat content? We studied 272 moderately obese subjects who had normal gallbladder ultrasonograms. The 900 kcal/day liquid diets contained either 16 g fat (N = 94) or 30 g fat (N = 178) each day for 13 weeks. A second gallbladder ultrasound was performed. Sixteen of 94 (17.0%) of the 16-g fat group developed stones with a weight loss of 18 (+/- 7) kg and a body mass index (BMI) decrease of 6 (+/- 2) kg/m2. Twenty of 178 (11.2%) of the 30-g fat group developed stones (P = 0.18, no difference in stone formation) with similar weight loss of 20 (+/- 7) kg (P = 0.08) and BMI decrease of 7 (+/- 2) kg/m2 (P = 0.04). Substantial fat for rapid weight-reducing diets resulted in gallstone formation. Since experiments have shown that our higher fat diet, containing 10 g fat per meal, results in maximal gallbladder emptying, cholelithiasis from rapid weight loss may not be solely attributable to gallbladder stasis.