If you're trying to lose weight, you'll find that martial arts make a fun alternative to getting in your daily HIIT workout.
Martial arts are an odd combination of cardio, high intensity exercise, and endurance training. If you've never practiced martial arts, you'll find that it can be a lot of fun to learn to kick, punch, and hit things properly. I found that it was one of my best ways to get in shape, and it definitely helped me get started down the road towards fitness.
Not sure which martial art to do to lose weight? Not all of them are created equal, and there will be some better for promoting weight loss than others!
If you want the best martial art to lose weight, boxing is definitely the one for you. You get in a whole lot of upper body work, which pushes your heart, lungs, and muscles no end. If you've never spent three minutes punching at an opponent in a ring, you've never lived. You feel like you're dying as you gasp for breath, and it's an exhilarating feeling as your muscles tire out in a hurry.
Kickboxing and MMA are very similar, and they're both quite good for weight loss. The fact that you do a lot of kicking means that your legs get nicely shredded, and you do a whole lot of cardio. Your arms are involved, and it's excellent for weight loss. It's harder on those that are overweight, so it may not be as good for beginners.
Definitely one of the best martial arts to help you lose the last few pounds and start getting in amazing shape, but those with 10 to 20 extra pounds on their body may find that it's just not physically possible to advance quickly. It's not an art for beginners, but it's an amazing discipline that will help you get in excellent shape once you've started to slough off those pounds.
Great: Taekwondo/Kung Fu/Karate
This is a great martial art even for the seriously overweight, as you start out nice and easy with the basic kicks and punches. They're all fairly simple arts at the beginning, but they get more and more active with each new belt. You'll spend a lot of time practicing forms, weapons, and combinations that won't give you the same amount of exercise as you'd get sparring, but it's a good place to get started with martial arts in general.
These martial arts are very good for self-defense, but they're not quite as good for weight loss. They involve a lot of wrestling, which is definitely great exercise--but which doesn't focus on shedding fat. There's a lot less jumping, kicking, and punching with these martial arts, where the main focus is on grappling, locks, and taking the opponent down.
Good: Krav Maga
Krav Maga has one purpose in mind: incapacitating your opponent in as few moves as possible. That means there's very little in the way of jumping around, kicking, and throwing punches, when a few short strikes to vital points will do. It's good exercise and a whole lot of fun, but it's not quite as good as some of the more active martial arts listed above.