We recently had a Bikewise week in New Zealand, a health promotion thing to encourage people to get on bikes, so you could enter the amount of miles/km you did and compare it to others in your workplace and around the country. So I really upped my mileage on my commute in and home again by doing on average around 50% more than I usually cycled, taking different routes, longer ways around etc...The increase in fitness and weightloss was actually pretty impressive. Afterwards though I found it difficult to keep up the motivation - but I'm working on it.