It can be fantastic for people who are smoothing out that last wee, tiny, bit of chub...and it is awesome for building flexibility and suppleness. And when part of a good diet and a comprehensive exercise regime it can produce some great results.  But a fat-burning exercise it is not. They like yoga because it seems easy ie: you stay in one spot and don't have to run, walk, lift heavy things..etc. Plus, because their fat does get in the way they NEVER actually are able to really do any of the poses that actually, really, work the muscles. Plus, they simply can't maintain the poses for a sufficient amount of time. It's just a psych game for them.."I'm healthy! I do fat yoga! Then I reward myself with a 1200 calorie, sugar-ridden, smoothie!"