That's about the distance for my commute too, but I have worked out a whole load of alternative routes home ranging from 10km to 25km (7 miles to 15 miles or so) and try to do those 2-3 times a week. Or more if it's a good week. I like the fact that I can get to work in almost no time -- it's much quicker than using public transport -- but that I can also take my time getting home. As for losing weight, it's only been a pound or too, but I don't have to worry about what I eat. In fact I've been scarfing down good quality Belgian and German chocolate all week. Mmmmm.