Celery
 

I heard that celery reduces your weight because it actually takes more energy to eat and digest than you gain from it. Anyone know if this is true or know of any similar foods?

Yes, it is true.

Same goes for water colder than your own body's tempature. You will actually burn calories heating the water to your own body temp. Not anything significant, but it's a neat idea to think about.

1 mL (or gram) of water heated 1 degree C is one calorie. 1000 calories = 1 "dietary" Calorie (or Kcal). So, 1 L of water heated 1 degree is 1 Calorie.

Body tempurature is 37 C. Cold water is about 4 C. That's 33 degrees.

Drinking 1 Litre of water thus costs you 33 Calories, unless you where already overheating at the time.

Just be warned not to drink very cold water when working out. That can cause problems.

Negative Calorie Foods

The site explains that while the foods don't have negative calories themselves, they cost more calories to fdigest -- mmmm --OI could live on mango salsa....

Some of the foods, they claim are negative calorie
These are some of the foods on his list:

Vegetables

asparagus
beets
broccoli
cabbage (green)
carrots
cauliflower
celery
chicory
chili peppers
cucumbers
endive
garlic
lettuce
onions
papayas
spinach
turnip
zucchini

Fruits

apples
cranberries
grapefruit
lemons
mangos
oranges
pineapple
raspberries
strawberries
tangerines

LOL ive heard this about lettuce before but always thought it was a myth