Hi there! I am not a fitness expert, but I have been doing Yoga for a few years and I don't think it would be a waste of time for ANY body type.
Yoga is awesome for flexibility, strength, weight loss and overall well being. It also relieves back pain and tension. If your goal is to lose weight, I think you may have to add cardio along with weight training, as Yoga alone may not be enough to shed pounds (please consult a fitness expert on this to confirm as I don't want to give you incorrect info). It will however sculpt some nice muscles while holding all those poses (plank, side plank, warrior 1, 2 ect) which do lean you out and help rev the metabolism.
Even if you only do Yoga 1 or 2 times/week, I am sure you will notice the benefits and continue to use it as part of your fitness routine.
Natasha