"fat lazy" is a stereotype. I see people of all shapes, and sizes driving a car to work, & I've seen people of all shapes and sizes riding bikes.

Do Bicycles Make Better Employee's, Commuters?
 

I said it once, and I'll say it again....Heck Yeah!

I have to admit, I'm a horrible employee.
Read bike forums all day and talking to my coworkers about everything else but work.

I have a surprising amount of free time at work... but I can say for sure that I'm on average in the office for a full hour longer every day that I ride in than I am if I have to take the subway... I leave at the same time either way, and I can outrun the train pretty tidily ;)

From my experience, I find that I am a more productive worker during the stretches during the year when I commute by bike, even though I am probably at work for a little less time per day. I commute by bike two-three times a week during the spring and summer, and not at all during fall and winter. On the days that I ride, I feel invigorated and more focussed. I also know that I have to get my work done, because I typically leave a few minutes earlier to offset the slightly longer commute time home. (It's 70 minutes by bike; 50 minutes by metro.) During the season when I do not ride (or otherwise exercise), I feel sluggish at work.