Get to breakin! I'm sorry bboyin (cardinal sin around here apparently

)
It's exellent cardio. Practically everyone I know lost weight from breaking (bboying, shit sorry). Be aware, especially if you carry a lot of weight on your hips, that your footwork may have a tendency to look a little heavy initially. Try your best to stay on your toes and not flat foot, that will help. Stay on top of your hips or, if you are behind them, really think about raising them, don't let them sag down. I see this a lot with bgirls and it really contributes to making them look heavy and slow. Damn lower center of gravity!
Personally I practice for however long I'm feeling it that day. Sometimes it'll be a few hours, others just 15 minutes. Just enjoy it and have fun with it; that's what keeps me coming back. As long as you have some consistency you should see improvments fairly quickly.