Agreed. It's remarkable - My weight has varied between 160 pounds and 210 pounds, and almost has 100% correlation with a single factor - whether I was carpooling or walking into work. Diet, secondary exercise, type of food I'm eating - none of them seem to have anywhere near the causative impact as just simply walking 25-30 minutes into work (and back) each morning. Every morning. Every Day. For months on end.

I have friends who mock this, and talk about how much more important it is to get into their peak-heart-rate on their at-home treadmill. That they've actually used maybe a couple dozen times.

I don't have a choice - have to walk to work. And Back. 3 1/4 miles a day. Every day.

That's almost a marathon a week. :-)