I'm biased but I tell everyone I know if they want to truly lose weight, i'm not talking few pounds - literally have it melt off - join a MMA gym, and eat clean. I sound like a broken record.
1. Vast majority don't have the will power to push themselves to tipping point during work outs - in a MMA/ Crossfit gym you are surrounded by people and will be called out if your slacking - meaning you will always get pushed harder, then you would push yourself.
2. Your in a team environment, accountability helps keep you on track for your goal. Doesn't hurt surrounding yourself with some health nuts few times a week.
3. High intensity training, is known to burn crazy amount of fat, and help with hormone levels.