Median time spent commuting to work increased from 24.4 minutes in 2000 to 25.0 minutes in 2006, for the nation. You might guess SD is different but it is not. In 2006 the median commute time was 24.9 minutes.
http://factfinder.census.gov
It’s true that weight gain/loss is completely dependent on the difference of calories in vs. out. I would add though, that what type of calories your “in” consists of will partly determine whether it is muscle or fat you will lose/gain. If you ate 1000 calories of lard a day while burning 1500, you would be more likely to lose muscle than fat. If you ate 1000 calories of tuna while burning 1500, you’d be more likely to lose fat.