Negative calorie

A food that supposedly burns more calories while it's digesting then how many calories are in the food.

Examples...

Asparagus * Fennel
Aubergine * Gourd *
Broccoli * Leek
Cabbage * Lettuce *
Carrots * Marrow *
Cauliflower * Peppers
Celery * Radish *
Chicory * Spinach
Cress * Tomato *
Cucumber * Turnip

I don't want to gain any weight from calories, I think I'll have some cucumber because it's a negative calorie food.