Which one of these plans would not be considered a "fad" diet? the grapefruit diet (where you eat grapefruit with every meal) atkins (very low carbs, high on protein and fats) weight watchers (you can eat anything, but count total calories) a diet where you can only eat certain foods at certain times of the day 4.?

First you have to know what a "fad" diet is. A fad diet is a weight loss plan that over-promises dramatic results. These diets typically don't result in long-term weight loss and they are usually not very healthy.

That being said, Adkins, Weight Watchers, and only eating certain foods at certain times are all considered fad diets. That would leave the Grapefruit diet as the only non fad diet, since it does not limit your intake of any certain foods, just adds one to your meals