The Zone Diet places special emphasis on the moderate intake of low-fat protein, low glycemic-load carbs (such as those found in fruits and vegetables), and monounsaturated fats, as well as all needed nutrients.
Ayoob: "This one is fairly moderate, focusing on a good amount of lean protein, moderate fat and moderate carbs. Skip the vegetarian version if it's not your thing."
Katz: "I think this is too high in protein. It works by providing a strict dietary discipline, but suffers the same problem with sustainability as the others."
Ikeda: "Another oldie that had no impact whatsoever on the obesity epidemic in this country."
What It Is: Despite the names of these popular diets, both the Cleveland Clinic and the Mayo Clinic deny having any association whatsoever with them. This, however, does not seem to have impacted the popularity of either of these regimens, both of which are subjects of a high volume of Internet searches by those hoping to lose weight.
The 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 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 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."