Gallstones seem to form in response to a number of factors, including body chemistry, body weight, gallbladder motility and perhaps diet.
Cholesterol gallstones form when the bile contains an abnormally high proportion of cholesterol in relation to bile salts. In addition to this infrequent or incomplete emptying of the gallbladder may result in overconcentrated bile, and the bile may contain proteins which promote or inhibit cholesterol crystallization into gallstones.
Obesity is a major risk factor for the formation of gallstones, probably because obese people tend to have large amounts of cholesterol in their bile, low levels of bile salts and inadequate gallbladder emptying.
In creased oestrogen levels also seem to play a part in gallstone formation, probably by increasing cholesterol levels in the bile and decreasing gallbladder movement and emptying.
Prolonged fasting and very low calorie diets also seem to promote the formation of gallstones.
The relationship between gallstones and diet is not clear, but their formation may be favoured by a low fibre, high fat diet.