Dude, you are ignorant of nutrition then. 300 kcals is roughly the energy needed for a person to run 3 miles.
It does take 1 calorie to raise 1 gram of water 1 degree C. However, it takes 1 kcal to raise 1 kilogram of water 1 degree C. 1 gram of water is ~ 1 milliliter, not a lot when you are talking about the human body.