The so-called Cleveland Clinic 3-Day Diet features a strict menu which is heavy on black coffee and light on calories. Proponents say those who follow the diet can lose up to 10 pounds in three days. The so-called Mayo Clinic Diet, on the other hand, features a great deal of grapefruit juice and few, if any, carbs.
Ikeda: "If these diets worked, the Cleveland Clinic and Mayo Clinic would proudly take credit for them. They would publish books about them and make money off the sales. The problem is, these institutions are too ethical and know the diets don't work, so they distance themselves for good reason."
Katz: "These look ridiculous; they simply provide a detailed meal plan that restricts calories. As soon as you stop following these detailed directions, it's all over."
Ayoob: "First, skip any 3-day diet. If it's not meant for more than three days, you're likely just maximizing water loss, not much else. Go off the diet, the water weight returns and you've lost three days that could have been spent working on sensible eating. ... Any diet that only lasts a few days or a few weeks is a diet to be avoided. Better to get on some sneakers and do a fast walk away."
What It Is: While no one definitive grapefruit diet exists, all are based around a low-calorie approach, combined with a lot of grapefruit and grapefruit juice. The inclusion of this fruit is based on the idea that grapefruit contains a certain chemical or enzyme that aids weight loss.
Most of these approaches are short-term weight loss diets, lasting anywhere from a few days to a little more than a week.
Ikeda: "I wonder how many vitamin deficiency diseases one could achieve by staying on this diet long enough. Quite a few, but rest assured it wouldn't be scurvy since we all know that grapefruit gives us the big [Vitamin] C."
Ayoob: "Back to the 'Mayo' diet, there are grapefruit versions of this, and the Mayo diet was also akin to the 'Cabbage Soup' craze in the '80s. Skip them. They're 10- to 14-day temporary fixes."
Katz: "Diets based on a single food work by restricting choice. But over time, restricting choice is incompatible with both health and dietary pleasure. Unsustainable."
What It Is: The South Beach Diet, developed by cardiologist Dr. Arthur Agatston, is a three-phase plan intended to help adherents lose weight in the short term and keep it off long term. Of the three phases, the first is the most restrictive, especially when it comes to carbs. Dieters are instead encouraged to include lean protein and high-fiber vegetables in their meals. Phases 2 and 3 gradually reintroduce non-refined carbohydrates and other dietary elements.
The diet plan also encourages exercise as a part of the diet, a feature that proponents say distinguishes it as a healthy lifestyle rather than simply a diet.
Ayoob: "This one is pretty moderate. Developed by a cardiologist, it's heart-healthy. It tends to penalize refined carbs. They're really OK; just watch portions and go for whole grains whenever you have the choice. It also focuses on exercise, and that's the other part of the diet puzzle. Activity -- you've got to have it, or the diet works a heck of a lot more slowly."