Kevin Hart Keto Reviews: As Ewoldt explains, a typical American diet consists of 50% or more carbohydrates, which convert to glucose in the body. But when you switch to a very high-fat, low-carb diet, your body, by necessity, shifts away from glucose and instead uses fatty acids and ketone bodies for energy. A cluster of symptoms called the keto flu typically kicks in a day or two after starting the keto diet, says Mancinelli, and come on as your body goes through carb withdrawal. As we…