Originally Posted by
HerrKaLeun
There is a lot of metabolism going on between the calories in the food you eat and the output energy of your legs. You also don't measure any core and upper body and heart and lungs energy.
With other words, depending an all the digestion and metabolism inefficiencies and auxiliary needs you could put out 500 calories out of your legs, but that may mean 2,000 calories eaten. Or 1,000, or 3,000.
There are some small differences in how one metabolizes different types of food but these are 2nd and 3rd order effects that don't really explain why people gain or lose weight. The majority of Americans just eat too much by a significant amount.
My experience has been that over a period of weeks/months if I carefully count Calories in and out that the resulting weight loss is very close to predicted. It doesn't work very well at the daily level as changing the sodium intake will result in large weight swings due to water retention but these cancel out over time.