I ran across this fascinating experiment, in which a young, fit man compares two diets consisting of vastly different macronutrients: 5000 calories, over a period of a month, meticulously recorded. If the "calories in, calories out" theory is correct, he should have the same result both time--a predictable weight gain. In fact, that's not what happened.
The second half of his experiment (low fat, high carb) is ongoing. During the first half (HFLC), he gained a little over 2 pounds, and lost 3" off his waist. So far, one week into the LFHC experiment, he's gained 7 pounds and added 2 inches to his waist. Preliminary results suggest not all calories are created equal. You can follow him here:
http://live.smashthefat.com/5000-cal...allenge-day-7/