The Scarsdale Medical Diet is a low-fat, low-calorie weight-loss diet system and accompanying book (The Complete Scarsdale Medical Diet plus Dr. Tarnower's Lifetime Keep-Slim Program) by Scarsdale, New York physician Herman Tarnower.

The Scarsdale Medical Diet specifies a very specific and structured diet that is to be followed exactly for the first 14 days, another 14 day period follows that still specifies certain foods to eat, but is less structured and allows additional foods. A grapefruit for breakfast each day is meant to supply enzymes necessary for burning the 700-calorie per day diet. Artificial sweeteners are used in place of sugar.

Critics acknowledge that the diet gives quick results but say that weight loss on the plan results simply from the reduced caloric intake, and is mostly water weight that is quickly regained; in addition, critics argue that the diet is so extreme as to be unhealthy. However, many followers of the diet report positive results.