Unfortunately most weight loss diets are actually fad diets. All to often diets that describe themselves as being new or revolutionary are actually diets that are twenty or thirty years old come back for a second or third wave of popularity. Good examples are the Zen diet, which is simply a revival of hippie macrobiotic eating theories from the mid 1960s, the Zone diet which is based on food combining principles that have been around since the turn of the 19th century and the Atkins diet which was initially pioneered in the 1970s and had a Gloria Swanson type comeback not too long ago.

The best way to identify a fad diet is to determine if it is based on any of the following principles:

It is based on the way Neanderthals eat
It is based on foods from the bible
It is based on your blood type
It is based on eating mostly protein and no carbs
It is based on eating mostly carbs and no protein
It is based on eating no fat
It is based on eating fatty foods
It recommends the eating of negative calorie foods
It recommends eating only one fruit such as grapefruit
It recommends drinking more than three cups of coffee a day
It claims that you can eat whatever you want

Perhaps the most popular of these diets are the High protein/low carb diet that are based on the idea that carbohydrates are bad, that many people are "allergic" to them or are insulin-resistant, and therefore gain weight when they eat them. This includes the South Beach Diet, the Zone Diet and the Atkins diet. These types of diets induce ketosis to accelerate weight loss. Ketosis is an abnormal body process that occurs during starvation due to lack of carbohydrate. Ketosis causes fatigue, constipation, nausea, and vomiting, none of which are part of a healthy lifestyle. Long-term side effects of ketosis are documented to include heart disease, bone loss, and kidney damage

The truth behind weight gain in this society is that people are eating more total calories and getting less physical activity. Your body simply doesn't distinguish between types of calories when it comes to weight gain or loss only the number of them.

Crash diets dehydrate you, low calorie diets put your body into starvation mode so you plateau so you can't lose one more pound and high protein diets stress your kidneys and clog your arteries.

The truth is that you do need protein and fat in the diet, both serve important metabolic and physiological roles in the body. Fad and crash diets, such as the ones described above are not only unhealthy but they are also cause rebound weight gain. Also most diets, even though diet gurus write them cause an initial weight loss but the ultimate result is that you gain all of the weight back the minute you go off the plan. If you don't gain it back within a couple of diets, you are likely to gain it all back plus a bit more within a year.