The only way I worry about weight is that I always want to see a higher number on the scale, so long as my bodyfat stays a single digit %. I swing heavy sledge hammers, do planche pushups (a handstand pushup, only the body is horizontal instead of vertical), pinch grip pullups, hit a heavy bag, etc., and I always try to take in over 3,000 calories a day, the more the better, as long as it's not all junkfood
Any guys who want a decent muscle mass (nothing huge though..) and low bodyfat should try a routine something like this.. You'll be deceptively strong and have a good foundation in muscle to enjoy after a few months, and you only need like 30-45 minutes a day to maintain it well. The best part of doing the real-world motions is that you can have half the muscle of a bodybuilder and still wreck them in something like mercy or arm wrestling because your muscles will be used to movements like that, not just the standardized movements made while lifting freeweights.
Oh yeah, if anyone has an anorexic/bulimic friend, inform them that starvation drops their metabolism to barely above sea cucumber, and if they promise to eat at least 1,200-1,500 healthy calories a day, then you can promise them them they will lose weight faster than through starvation while maintaining a much better sense of well-being. It sounds kind of generic to say it like that, but if you word yourself right and use facts, then I know from at least one personal experience with a friend that someone will listen and hopefully turn their life around.