Honestly, I think the reason most authors tend to have so much success with the new fad diet of the week is that for the month or whatever that they run the diet, they're actually monitoring their food intake and making an effort to eat more balanced meals.

The diet itself seems almost irrelevant. Just the simple act of paying attention to what you eat (counting calories is an excellent starting point) will help more than anything, as you'll more easily recognize poor trends in your food choices, and the awareness will encourage you to diversify your diet.