Is there really any food which has zero calorie in it ? Well, in our diet,all food contain some amount of calorie, its just that it needs more calorie for its break down

There is still not any scientific evidence proving this.

There are some low nutrient and high cellulose food like cabbage,beets,celery which consumes slightly more energy to digest it than it nutritionally provide to the body.

These type of food generally consumed for weight loss program. Thus relieves the hunger without intake of calorie.

But these type of food for long term diet may result in malnutrition.

There are some effective diet pills which even helps in weight loss as well as do not tend to result in malnutrition.