well I have direct experience in using aggressive inline to lose weight without proper nutrition and I think liftbig is right. I kept my leg muscles but EVERYTHING ELSE went. I had 11 inch arms briefly (and like 22 inch thighs). Skateboarding and aggressive inline are VERY catabolic potentially because you do them for hours at a time (cortisol) and they are very damaging to your muscles.
If you're trying to lose weight/fat, then burning extra calories with skateboarding is cool but you need to have some nutrition timed around it: protein and some low gi carbs beforehand, and a little bit of something with protein every hour or 1.5 hours after that, and some more protein and carbs post-workout. skateboarding burns an insane amount of energy so you won't overcompensate unless your postworkout meal is a pint and a half of ben and jerry's.
seriously be careful, I lost 45 pounds this way without good nutrition and i was still 13 or more % bodyfat at 172 lbs bodyweight at 5'10.5" with those sexy 11 inch arms