Negative food?

I've been reading a lot about foods that produce negative calories. I know you're thinking how the hell can food have negative calories? Well the theory is that the food has such a low calorie count and it takes more calories just to digest it that it results in you actually burning calories by eating the food. I'm not sure what I think about that. The two that make a lot of sense to me are lettuce and cucumbers.

However, if you think about it, if you ate pounds and pounds of cucumbers I guarantee that you would gain weight. You would be really sick as well. Here is the list of possible negative foods. Just remember this is without the butter or sugar added in addition to the food in its natural state.

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

Fruit:
Apricot
Mandarin orange
Blackberry
Melon Canteloupe
Blackcurrant
Peaches
Clementines
Plums
Damsons
Raspberry
Grapefruit
Rhubarb
Guava
Strawberry
Honeydew Melon
Tangerine
Lemon
Watermelon