Fit for Life is a diet and lifestyle book series stemming from the principles of orthopathy. It is promoted mainly by the American writers Harvey and Marilyn Diamond. The Fit for Life book series describes a fad diet which specifies eating only fruit in the morning, eating predominantly "live" and "high-water-content" food, and, if animal protein is eaten, avoiding combining it with complex carbohydrates.
While the diet has been praised for encouraging the consumption of raw fruits and vegetables, several other aspects of the diet have been disputed by dietitians and nutritionists, and the American Dietetic Association and the American Academy of Family Physicians list it as a fad diet.