Obesity contributes to gallstones (1). Eating 5 ounces of nuts per week reduced the risk of gallstones by 25%.

1. Edward L Giovannucci et al, Prospective study of abdominal adiposity and gallstone disease in US men
Am J Clin Nutr 2004 80: 38-44

Conclusions: Our data suggest the presence of a significant association between abdominal adiposity and the incidence of symptomatic gallstone disease. As measures of abdominal adiposity, abdominal circumference and waist-to-hip ratio predict the risk of developing gallstones independently of body mass index.

2. Edward L Giovannucci et al, Frequent nut consumption and decreased risk of cholecystectomy in women
Am J Clin Nutr 2004 80: 76-81

Background: Gallstone disease is a major source of morbidity in the developed countries. Nuts are rich in several compounds that may protect against gallstone disease...Conclusion: In women, frequent nut consumption is associated with a reduced risk of cholecystectomy.