[aruanan]

I don’t really disagree with what you’re saying, however, there seems to be something else at work. Maybe my skinny husband really doesn’t eat anything (altho he sure appears to). I know what we were taught, I also know that it doesn’t always jibe with reality.

Like almost anything, there is a Bell curve distribution. I'm sure on one end there are folks whose resting metabolism is a bit more active and on the other those whose RMR is a bit less active and all the rest of us are distributed in between. When you're younger, you have a greater ability to spontaneously adjust activity level to energy intake and vice versa. This ability appears to diminish with age; however, the necessity of physical activity often diminishes with age together with the opportunity for it. The body appears to need at least a certain level to effectively count calories, so to speak, and make adjustments in activity or appetite to maintain homeostasis in body weight/composition. The weight creep of 20-30 or more pounds that most people experience between their 30's and 50's comes out to a very, very small number of kcals per day, showing that otherwise, the match of energy intake to expenditure is pretty closely regulated.

[brytlea]

When you're younger, you have a greater ability to spontaneously adjust activity level to energy intake and vice versa.

That's interesting, must be research newer than when I was still involved in the field. We were taught that as you age muscle mass diminished and because muscle takes more cals per pound, you could eat less without weight gain. I have not kept up with the newer research as I have been out of the field since the early 1990s and while I do read things I run across I wouldn't call that keeping up.