One food diet

One food diets are based on 1 single food e.g. grapefruit, egg, poultry, melon etc. Dieters are allowed to eat as much as they like of their chosen food, but other foods are either prohibited or severely restricted. The diet is usually supplemented with multi-vitamins and dieters are advised to drink plenty of fluid. Nevertheless, one food diets are potentially dangerous if taken for a long time. Despite supplementation, it is virtually impossible to obtain a proper balance of nutrients from one food.

@Anju
Food groups mainly consist of carbohydrate, proteins, fats and oils, sugars and fruits and vegetables. One food diets are based on one particular group of foods. They are basically advised to lose weight.Initially, weight loss will be there but in the long run it is not advisable. As in the long run, nutrient deficiency will be there. so ideally having a balanced diet , low in calories and rich in nutrients is good for long term weight loss.

I agree with Aprupa. These are all fad diets that just give you a temporary weight loss. You can't have it forever. Thus as soon as you revert back and start having all the foods in your diet you immediately start putting on weight.