So what do we do about it? We join a gym or jog. But the problem's not lack of exercise. It's lack of activity. There's an important difference.
Just being alive requires energy — for me, around 2,100 calories a day. But I have a pretty active lifestyle and get through 2,700-3,000 calories a day, just through teaching, running around the studios and being on my feet.
If I was trying to burn off those 600-900 extra calories by working out, I'd have to train for a couple of hours every day. Instead, I do it just by showing up to work.