I was average at 165 pounds 5"11 (male). I lost nearly 20 pounds last year going down at the worse to 145 pounds which in my opinion is way too low. So I started eating more (taking protein supplements because I'm not hungry enough) and now I'm staying at 152 pounds average and building (leg) muscle!!

I don't go to the gym anymore; it would still be good for the upper body and core workout though but I don't want to have to go there. For cardio it's definitively enough for me. I use my commute as a training ride (10.5 miles each way); adding intervals and stuff like that when possible (still have to stop at red lights ). I commute 2 - 3 times a week and trying to augment this to 4 - 5 times a week. I feel that if I'd take is easier I could do 5 times a week. But right now I'm trying to balance it out with rest days instead and work harder. It's a balance between hard workout and long term endurance I guess. So I say yes, there's definitively a way to incorporate a structured workout in the daily commute.