[Toddsterpatriot]

e.g., x calories burned per mile of swimming, x calories to consume per pound of weight gain or loss.

You might have to walk more to burn the same calories, the calories still balance.

3 guys eats 2000 calories a day. One burns 1900, he gains weight. One burns 2000, he remains the same. The third burns 2100, he loses weight.

It doesn't matter if the different amounts burned are because they exercise differently, their metabolism is different or their hormones are different.

Eat more than you burn, you'll gain weight.

[9YearLurker]

Not wanting to be too crude here, but there is also the factor of how much is kept in the system to be burned or stored—and how much is passed on through. Both the option to burn or store and to pass through or use are probably affected by more factors than we’ve yet come to fully understand.