Without the guidance of a physician, trendy diets may have harmful effects, as these types of diets tend to be nutritionally unbalanced. Take the no carb or low-carb diet, for example. This diet is low in carbohydrates, but can be high in fat and protein. Diets that are high in fat but low in carbohydrates can cause a deficiency of the enzyme carnitine palmityl-transferase II (CPT II). This deficiency may lead to rhabdomyolysis, the breakdown of muscle tissue, which can be harmful to the kidneys. Diets high in fat can also raise cholesterol levels, which increases the risk of heart disease. Eating too much fat also increases the risk of getting breast cancer and can trigger symptoms of irritable bowel syndrome in some people.