A fad weight loss diet is any diet which promises fast weight loss without a scientific logic. Fad diets mostly eliminate entire food groups and hence do not provide a wide range of important nutrients.

Fad diets provide short-term results and are difficult to sustain and lead to serious health problems on a long term basis. The best approach to weight loss is to follow a long-term, healthy and balanced eating plan and to exercise regularly.
Weight loss and fad diets:
Diets that encourage fast weight loss generally have little effect on body fat. The initial weight lost from fad diet is mostly water and lean muscle (which is generally not desirable).
When we cut down on food drastically, the body begins to break down muscle to meet energy needs. Muscle break down to release energy is faster than breakdown of fat stored in the body, which is not the desirable route to weight loss.
Breaking down muscle leads to:
• a loss of water, creating the illusion of rapid weight loss
• a reduced metabolic rate, so when the diet is stopped it is much easier for the body to gain fat than it was prior to going on the diet.
As a result, with loss of muscle, our body will become fatter over time.
Fad diets often encourage a short-term change in eating behavior, rather than encouraging changes that can be sustained in the long-term basis. It is essential that diet should meet nutritional needs, and is practical and suitable for individual lifestyles.