How do I lose muscle mass?

It takes 72 hours of inactivity for your muscles to start to atrophy

Too bad 2 years isnt doing the trick

How bulky are you? How long have you been running high mileage? A few of the best distance runners out there are pretty big, relatively speaking (e.g. Ben True, Chris Solinsky. As long as you're not huge, I wouldn't worry about it too much. Focus on upping your mileage, staying healthy, and eating well but not too much and you will eventually shed some muscle. In the meantime, I bet you'll run just fine.

Triple you time on letsrun.

Burn more calories, eat fewer calories. Simple!

"I find not eating helps."--Gary Oldman on his weight-loss-for-a-role technique.

would eating less protein than you need help?

i'm under the impression that your body cannibalizes itself for protein if you don't give it enough. run more and eat less protein.

in all honesty i was in the same place this guy is and cutting back on protein while upping mileage and intensity has definitely helped me lose upper body muscle.

if this is wrong someone please tell me.

Well the thing is, you want to lose upper body mass, but not compromise recovery. Hard workouts cause micro-damage to the muscle cells in the legs. You want to be sure all the building blocks are available for the legs to quickly repair themselves. Having said that, most people eat more protein than is needed. I think it would be better to restrict calories in general, but nothing drastic or your running will probably suffer more than it does from a few extra pounds of muscle.

You will probably never lose all of it. I weighed 150lbs in college, quit running and took up lifting weights. Bulked up to 200 lbs of muscle before realizing 1.) I looked stupid and 2.) It wasn't condusive to playing sports (basketball/flag football etc). Anyway, when I was like 27 I decided to get back into running. I run a decent number of miles (although inconsistently) and cannot get below 175. Bottom line, I regret ever putting on mass as I am convinced I will never be able to reach my potential as a runner, largely due to the muscle mass that just won't go away.

All that said I do look a lot better than the average 135lb runner who is beating me in races by a couple minutes.

Dude, flag football is NOT a freaking sport.

Only a geeky runner would worry about his flag football skills...gawd...

Long runs of over two hours. Once you are done burning glycogen and fat, your body turns to its last resort: muscle. Watch out for ketosis though.

Get married. Fa true, I lost 15lbs the first year.

You could also start eating bran cereal with skim milk for dinner more often.

Lance proved that the best way to lose muscle mass is to get serious cancer.

Sort of true. But when you are being thrown on the offensive line with the fat dudes it is a bit of an eye opener when you used to have 50.xx 400 speed.

He's defending playing flag football.