Here's some food for thought in regards to the setpoint theory and calorie counting. It is my contention that the setpoint theory is an attempt to explain why calorie counting has such a horrible track record as a weight loss method.
Assume an average person consuming 2,000 kcals per day. That's about 750,000 kcals per year. Now, current caloriecounting theory states that fat cells grow or shrink at a rate of 3,500 calories per pound. That is to say, a calorie surplus of 3,500 calories, in excess of basic metabolic needs, will result in the growth of a pound of bodyfat. The same goes for a calorie deficit.
Are you with me? A pound of bodyfat = 3,500 calories. In theory. Our average person is consuming 750,000 calories per year.
Question: When calorie counting, how accurate would this person need to be in order to maintain their current weight? Plus or minus 5 lbs. per year?
Consider that the vast majority of people do so without even counting calories.
Answer: They would need to accurate to within 48 calories per day. That's 2% accuracy. Outside of a laboratory that, ladies and gentlemen, is impossible. Misjudge that ice cream by 1 tablespoon and change the amount of walking done by 10 minutes and already it's off by that much. If Burger Boy puts an extra halftablespoon of mayo on the sandwich, calorie counting for the day is screwed. And what if that chicken is 6 ounces instead of 5? Oops, thats 50 calories difference.
Does anyone think that a triathlete like Eugene Allen can calculate his calories expended to within a 2% degree of accuracy? Over the course of the 3,000 or 4,000 or 5,000 calories he may burn in a day? Eugene, how much has your weight fluctuated from yeartoyear?
Is there a selfregulating system within the body that  under normal circumstances  keeps bodyweight relatively stable? The math suggest there is. Again, consider the assumption that MOST people don't gain or lose weight at a high rate, usually 5 lbs. a year or so over the course of their lifetime. So, if caloriecounting is so critical to achieving ideal bodyweight, then how is it that so many people who DON'T count calories manage stay within 2040 lbs. of their ideal weight for decades on end?
No one, maybe not even most labs, can calculate BMR and daily calorie expenditure and daily calorie intake to within a 2% accuracy. Yet that is exactly what the caloriecounting nazis like the American Council On Fitness and Nutrition are asking people to do.
