Fad diets usually become popular because they actually will work to lose a few pounds short term. Marketers are aware of this so they'll push and advertise a fad diet aggressively and then just move on to the next fad diet. This is one of the causes of yo-yo dieting. If you think back a few years you might remember the Atkins diet, then the cabbage soup diet, and then maybe the apple patch diet, this list can go on and on. What all these diets have in common is three things. They work short term, they're highly restrictive, and they fail long term.
The fact that they work short term is actually tied to their restrictive nature, which in turn is tied into why they end up failing long term. For example, the Atkins diet and other low carb diets highly restrict carbohydrates. For most people, the carb restriction alone will cause short term weight loss due to the fact they will not eat certain high carb, high calorie, non-nutritious food they had been eating like muffins, bagels, cookies etc. The weight loss though is a bit misleading. Because there is a switch from eating carbs to eating more fat, there is a change in the way your body holds on to fluid/water. The short term weight loss is actually just water weight and not fat.
Even worse than being mislead my short term water weight loss by the food and calorie restrictions in fad diets, is actually losing good weight coming from muscle. When highly restricting foods and calories, along with losing water weight, you might very probably lose muscle. If you lose muscle, your metabolism will slow and this slowing will make it difficult to lose fat weight long term.
When looking into a diet you should ask yourself if the restrictions of the diet can be maintained for the rest of your life. If these restrictions can not be held, then it's a fad diet and the short term weight loss is most probably coming from water weight, muscle and only some fat. Unfortunately this weight loss will rebound as soon as you return to your normal eating habits. Worst of all, the weight gain will probably be mostly fat because of the muscle lost during the fad diet. And like I said before, this fat weight will be more difficult to lose because of your slower metabolism. For those of you that have been on that yo-yo dieting roller coaster, does this sound familiar?
Obviously I'm not a big fan of restricting foods and or calories. As I began to develop the Fat X diet I wanted to make sure that it was open to all foods but in certain groupings. In simple terms it's a less of this, more of that approach. Making the Fat X diet versatile as far as food choices also dealt with the long term problem of the fad diets. Since you can chose the foods that you like, it makes it easier to stick to long term than fad diets.
So in conclusion, if you want to succeed long term, stay away from highly restrictive fad diets and follow a healthy more versatile diet like the Fat X diet or any other diet that is healthy and you can maintain long term.