Fasting has metabolic health benefits independent of what you are eating during your feeding periods. However, fasting will not turn a junk food diet into a good one.
In a study of people practicing IF and eating either a regular (25% fat) or high-fat diet (45% fat), Dr. Krista Varady found no significant differences in metabolic health between these two treatment groups over time. Each group displayed similar decreases in weight and coronary heart disease risk factors including LDL cholesterol and triglyceride levels.
Varady is currently exploring whether there are any links between fasting, low-carb diets and improved metabolic health. Many people who practice IF pair their fasting schedule with a ketogenic or very low-carb diet. However, there is little scientific research from human trials to determine any benefits or issues of pairing these interventions. The problem with ketogenic dieting is that it often leads people to eat an overabundance of unhealthy animal fats as opposed to healthier plant fats.
“I’d recommend eating your typical American Heart Association diet, or a balanced diet of protein, carbs and fats,” Dr. Krista Varady says.