What It Is: While these exists no one definitive grapefruit diet, 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 C [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."
Katz: "Surprisingly silly and short on substance, given the size of the following: cut out a lot of foods, add some back, then add some more back. At that point, if you start regaining weight, cut them all out again..."
Ikeda: "Where are the sequels? I'm waiting for the 'North Beach Diet,' the 'West Beach Diet,' and the 'East Beach Diet.' Or perhaps we need an 'Any Old Beach Diet.'"