What's better for losing weight, yoga, arobics or gym?

A combo....arobics AND gym. Do the strenght training to help build muscle mass (and burn a ton of calories!) and add the areobics, or any other type of cardio, to draw upon the fat deposits stored in your body.
One addition, that is very important! Diet! Try and keep your daily carb intake to between 280 to 320 grams. Fat to between 30 to 40 grams (none of it trans fat!) and have your bodyweight x 1.25 = the grams of protein you want, especially if you do some serious strenght training.
Good luck, and you should SEE results within a week. You'll feel them right away.

One, they all help. Two...

Being a personal trainer and in the gym every single day I see so many people doing so many things wrong. Then you see these same people getting discouraged because the results aren't following. So I'm going to let you in on a very important key to getting extreme muscle growth and weight loss without the use of drugs.eat healthy. consume a little more protein (meat) than usual. Drink a lot of water. Cut out all carbonated beverages, Coke, that stuff. Water is the best drink for you. It cleans out bodily toxins. Eat fruit daily, and veggies of course, fruit just tastes better haha. but vegetables are important too.Work out helps but having abs is about your body fat percentage. Eating healthy is the main thing, then work out. Two strengths when combined, result in that ab figure your looking for. When you work out don't do the same routine work out everyday. alternate between 3 days and do different things each of the three days. like Monday do crunches, Tuesday sit ups, Wednesday go for a run. then Thursday go back to crunches. You can do more than one thing a day certainly but don't do the exact same workout everyday. Your body gets use to it. Mix things up. Eat a healthy breakfast. Breakfast is the most important meal of the day. It gets you going. Eggs, bacon, milk, orange juice. that sort of thing are a good morning start to BREAK the FAST from the dinner meal until the morning. Just combine eating healthy with work out and you should see results in the first few days.

You have to come up with some type of a reward system, this will help keep you motivated. One of the best things to do is make a contingency contract. Stating what you want to do, who will help you do it, and what do you get for doing it.

Then also try to find a well balance diet program. My friend did this one diet program where the average weight lose is 7 pounds in 9 days. It might be the thing you are looking for, I know it's well balanced. If you want e-mail me and I can tell you more about either of these.