I'm in the VLC paleo camp and commute by bike 60KM round trip 2 or 3 times a week. It's mostly flat with a few nasty climbs. I consider it low level cardio (like walking) on the flats and HIIT on the hills. If your commute is all flat, make sure you get out of the saddle and race a few cars every once in a while.

15KM is nowhere near what some would consider chronic cardio, and if it's taking you an hour, you're probably not going all out. I think it could help you achieve your paleo goals.

Jump on that bike girl and pedal like you mean it :) I'm the opposite and on the gaining path, actually had to cut back on the amount of cycling as it was counter productive - it was a suggestion on a Paleo Hack and was spot on. Gain. Lose. Gain. Lose. Frustrating as all get out. I cut back on the cycling and now average about 20-30 miles a week v the 80-ish I was previously doing. In regards to my workout, currently it's 4 days split between CrossFit and weights and am back on the gaining path. What you're doing sounds great to me, I like variety and I think a body does too.

Just promise to always wear a helmet. I wear Rudy and feel it's the best brain bucket that you can buy - I love mine and when I had an Endo last year it literally saved my life. Head first into a power pole and I walked away - beat up as hell but alive. Any helmet will do, Bell and and Gyro are good and less expensive, but make sure it fits and you have it strapped on firmly. My PSA is done :) Happy cycling!

I would say go for it if you're NOT in a big city! I am, and I tried doing this once, but we get stifling heat and traffic jams... I.e. major stress. I gave it up and walked instead (my work was only a mile away, tho). I wish I could do it, I love biking. I find it very therapeutic.

If you feel fatigued/sore for too long after biking you'll probably want to add in some carbs.

Go for it! Helps boost the morale when you are at work. Just carry some baby wipes or the like so you can wipe down when you get to work.

Pros - Aerobic exercise, saving money on gas, being kinder to the environment, lowering stress before work, fresh air in the morning, burning off steam after work, sweet leg and abs workout, no stress/cost of parking, less wear and tear on your vehicle, increased productivity at work, enjoying your environment, meeting other fit people...

Cons - You get sweaty.

15km on a bike is nothing. You will hardly even be warm, and unless you are adding some HIIT sprints in, your heart rate wont get too elevated. If you are not trying hard to workout, riding is a fairly low impact exercise. Go for it. I love riding.

As a fellow bike commuter, I say rock it! Be sure to bring your office clothes and change into them once you get there, especially at first — I know that I surprised myself discovering how much I sweat when commuting. Past that, have fun and spread the good word of bike commuting!