What is a fad diet? A fad diet promotes an unhealthy way to lose weight. It does not consider the nutrients that your body is taking in, and it often results in serious health problems in the long run. Frequently, die diet programs offer drastic weight loss results that indeed help you reach your weight goals quickly. It is mostly not recommended by doctors as it disregards a healthy diet and proper nutrition. A healthy diet can also benefit your teeth, so be sure to keep things in balance.