Hans Eisenman

“An important insight has emerged from a series of simple studies that did nothing more than obtain ultrasound images of the gallbladder of people who had no gallstones at the start and who then initiated a diet of reduced calories, reduced fat, or reduced calories and fat. The ages of participants, proportion of females to males, strictness of the diets, and other characteristics differed across these various gallbladder ultrasound studies, but one thing they had in common was that as many as 55–62 percent of participants engaging in such diets developed gallstones; many of them had to go on to surgery to have their gallbladder removed. In short, cutting calories, cutting fat, or—worst of all—cutting both calories and fat sets you up for gallstones within a few weeks.11–14 The concept is simple: Consume foods with fats, and the gallbladder is prompted by the hormone cholecystokinin (CCK) to squeeze out the bile required to digest dietary fats. Reduce calories, fat, or both, and the gallbladder is left idle, having no opportunity to squeeze out its stored bile. Over time, bile crystallizes (bile stasis), the process that leads to gallstone formation. It is therefore well established that cutting calories and/or fat leads to high likelihood of gallstone formation.”
― William Davis, Super Gut: A Four-Week Plan to Reprogram Your Microbiome, Restore Health, and Lose Weight