I saw the movie WALL-E last night. I loved it, but of course was clobbered with the none-too-subtle message that our consumerist culture has made us fat, disconnected, and unhappy. (Because the movie so rightly criticizes the way we are burying ourselves in unnecessary junk and drinking billions of calories, it seems especially ironic that you can buy a plastic WALL-E cup with a built-in straw.) The movie takes place in the far-off future, but it's easy to see echoes of our modern commuter lifestyle.
I really noticed a big change in my life when I started commuting a long distance to work by car. I had been spoiled by living within walking distance to work for a long time. Once I started getting into that car every day, I put on weight quickly. I didn't even pick up the worst commuter habits: I never hit the drive-through on my way to or from work, I didn't usually eat at my desk, and I didn't start loading up on fancy coffee drinks. Our office rarely had food-related celebrations. I tried to get a walk in at lunchtime, even if it was to lunch and back. The biggest bad habit I picked up was eating lunch out most days. I also found it hard to find the time or energy to hit the gym. Plus, I was traveling a lot and had very little control over the food available to me at events. So, in less than a year, I put on 10 pounds of commuter weight to go with the 10 extra pounds I was already struggling with. I won't say that I left that job only because of the weight concerns, but it was one of the symptoms that I wasn't living the kind of life I wanted.
I am not sure how people who do this for long periods of time -- some do it their whole working lives -- don't pile on megapounds. There do seem to be some people who manage it. The only thing I can guess at is that they keep their diet very strictly regimented, and that they go to the gym every day, maybe on their lunch hours. Anyway, I give them a lot of credit, because it must be very difficult.