For one thing, it’s high in saturated fat, which has been linked to heart disease. Additionally, a nutrient deficiency and constipation could occur since the keto diet is very low in fibrous foods such as fruits, vegetables, and whole grains. Unlike some of the other popular low-carb diets, which typically are high in animal protein, the keto diet focuses on getting to the body to burn stored body fat instead of sugar as the main fuel. When body fat is broken down in the liver instead of glucose, s an energy byproduct known as ketones are produced. How often you eat while on a keto diet plan is also up to your personal preference.