It sure will if you do it right. Start out with a easy warm up for 10 min. Then start pedaling at 70-90 rpm's with just enough resistance to get your heart rate to 70-80% of your HRM ( Heart Rate Max ). You want to stay in that zone for max fat burning. A heart rate monitor will help a lot and keep you from overdoing it. You want a pace that you feel you can do all day. Toward the end of the ride you can pick it up a little and increase your heart rate. No matter if you are going uphill or down hill always pedal at 70-90 rpm's with a lite pedal pressure. Pedaling slow and mashing on the pedals will kill your legs quicky. If you need to catch your breath or your legs start to burn drop down a gear or two and keep going.
It will take a few weeks to see a difference and if you haven't riddin for a while take short trips until you get use to the saddle. Diet will have more of an effect on weight loss then anything else, it is too easy to out eat any exercise you do.
