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Although obesity is a well-recognized risk factor for gallstones, the excess risks associated with higher levels of obesity and recent weight changes are poorly quantified. We evaluated these issues in the Nurses' Health Study. Among 90 302 women aged 34-59 y at baseline followed from 1980 to 1988, 2122 cases of newly diagnosed symptomatic gallstones occurred during 607 104 person-years of follow-up. From 1980 to 1986, 488 cases of newly diagnosed unremoved gallstones were documented. We observed a striking monotonic increase in gallstone disease risk with obesity; women with a body mass index (BMI) > 45 [kg/m.sup.2] had a sevenfold excess risk compared with those whose BMI was < 24 [kg/m.sup.2]. Women with a BMI > 30 [kg/m.sup.2] had a yearly gallstone incidence of > 1% and those with a BMI [is greater than or equal to] 45 [kg/m.sup.2] had a rate of [is nearly equal] 2%/y. Recent weight loss was associated with a modestly increased risk after adjustment for BMI before weight loss. Current smoking was an independent risk factor; women smoking [is greater than or equal to] 35 cigarettes/d had a relative risk of 1.5 (95% CI 1.2-1.9).

Diet has long been suspected as an influence in the development of cholesterol gallstones, but its role in the disorder has not been studied well. The occurrence of gallstones was evaluated in a population of 88,837 registered nurses, all female, who completed questionnaires about nutrient intake before gallstones were found. During the four-year follow-up period, surgery to remove gallstones was performed on 433 women, and 179 women developed gallstones that were not removed. Increasing risk of gallstones was associated with increasing weight in the group, and weight gain was also a risk factor. Excess calories were a positive risk factor, while alcohol intake was observed to reduce risk, but these factors were more important in nonobese women. After adjustment for energy intake, the only dietary components that correlated with the occurrence of gallstones were vegetable fat, vegetable protein, and total fiber: high intake of these foods were associated with a lowered risk of gallstones. Fiber was more important among obese women, while the vegetable fat and protein were more important among nonobese women. Possibly, vegetable fat and protein altered cholesterol utilization or otherwise influenced gallstone formation. The study indicates that compared with the effect of obesity itself, diet plays a relatively minor role in the processes underlying gallstone development. (Consumer Summary produced by Reliance Medical Information, Inc.)