Atkins Diet can cause gallstones

Health 24 - Diet, Weight loss: "Negative effects:
Then there are the negative effects associated with the Atkins diet that may have started to influence public perception.
On individual level, dieters who stay on the diet experience negative effects such as constipation, foul breath, gout, nausea, gallstones, raised blood fat levels, deficiencies and kidney disease.
If these side effects don't put them off, many dieters find that they just cannot sustain eating only protein and fat for long periods. Once they stop using the Atkins diet, they tend to regain most of their hard-lost fat, and often gain even more than they lost in the first place."