Down hill biking

Biking uphill is much more difficult and you are likely to lose a lot more weight this way. If I were you I would concentrate on the actual exercise itself and not worry about whether it's downhill or uphill. In fact, unless you go up there is no way for you to come back down right? :) Get yourself a good course bike and all the gear that goes with (Just to make sure, you don't break anything) Once your all geared up find a good spot and start biking twice during the weekends. This should be enough to get you started.

Hey Geetanjali,
Downhill biking is a sport for agility training, weight loss, endurance training etc. Its a difficult sport using lots of energy. So its sure that you are going to burn a lot of calories. But make sure that your posture is correct and you wear proper footwear to avoid any injuries.