Keto Body Tone As mentioned before, Keto BodyTone is simply incapable of causing any adverse effects on the body. However, a keto diet can be quite painful as it changes the whole system by shifting the body’s fuel source from carbohydrates to fat. Symptoms of the keto flu include vomiting, nausea, constipation, indigestion. Because of these adverse effects of a keto diet, individuals stop following it much before it can show some sort of improvements.