Keto 6x Disadvantages of quick weight loss diets Fast weight loss eating plans have disadvantages. One of them is that persons shall regain the lost weight as soon as they stop the diet. What's worse is excess weight is acquired as a result of insufficient fiber also. Other health problems happen to be experienced such as for example heart disorders, constipation or irregular bowel motions, dehydration and malnutrition. There are persons who acquire gallstones also. It is necessary to talk to a doctor first before undergoing these diets therefore.