Lost about 5 lbs last week by cycling in the heat and humidity of summer. Down about 30 lbs in the last year. This is a small fraction of what I want to (need to) lose, but I am doing it slowly and sustainably so that when I achieve my goal I won't be yo-yoing up and down, it will be real and hopefully life-long.
If battling the bulge is the goal, commuting and cycling in general is just a small part of lifestyle changes that can help you achieve and maintain a healthy weight.