Fasting diets are nothing new and certainly not a fad diet. Fasting has been around for centuries. Sometimes it is used for religious reasons; as a means to detoxify the body, mind and soul.

Some fasting diets allow liquids such as broth and even juices; while others only allow water or tea. Some fasting diets don't even elminate food altogether but maybe only certain foods or just a drastically lower caloric intake.

Because of fasting drastically reducing the calorie intake is it actually harmful to your body?
Although fasting interferes with the function of healthy metabolism, it does not destroy your body's metabolism.

When you begin a fast, the body has no choice but to dip into the stored body fat. This may seem to work at first but after some time has passed, the body realizes it is not getting any food anytime soon. So to in order to continue to live off the stored fat it will become more conservative on burning the fat. So then the scale will not reflect any weight loss or fat loss.

Since fasting is only intended to last for a short period of time, most fasters cannot stick with suck a low caloric intake or no food intake, that they soon return to their previous eating habits. Having food all of a sudden doesn't have an impact on the body's conservation method. Since it cannot predict if you are going to deprive it from food again, it will immediately store the new food as fat. This is what causes dieters to gain weight back once returning to "normal" eating behaviors.

All of this back and forth between no food to having food may seem to screw up the metabolism but that is not the case. It will have a short term impact on how or when it will turn food into fuel or store into fat. Hence the weight gain when returning to a normal food intake.

The main concern with fasting is that you deprive your body of nutrients that are necessary to live each day.

Fasting for short periods of time is fine. And by short I mean 1-2 days. Fasting in the form of a restricted calorie diet has even shown to be beneficial for lab rats and people because it promotes longevity and can improve insulin levels. Although, there are certain health conditions that should never fast such as diabetics because of the huge dip i insulin levels that occurs during a fast. And of course a woman that is pregnant or breastfeeding or someone with chronic illnesses also shouldn't fast.