I walk between 10 and 15 kilometers a day. This game and a bunch of other stuff was helping to glue my arse to a seat so I did something about it. I've lost 12kg since Christmas. If I can do it anyone can. I have no cartilage in my right ankle and a very misshapen rib cage but rather than causing more problems, the loss in weight has helped my ankle, the muscles and ligaments in my foot and ankle have strengthened, and the weight loss has taken pressure off my ribs, which are still sore a year after my accident.
I walk to and from the train station every day, so that's 7kms minimum.
There's easy stuff you can do to avoid an early death or health complications, but your best bet is to work it into your day with minimum impact. Getting the bus to the train station and train to work used to take an hour and twenty minutes from home to work. Walking to the train station has dropped that to an hour.