Yes...Yoga is a very good workout. It poses stretches your muscles and increases your range of motion. By the passage of time body will be flexible.
If you practice regularly then it will help you develop muscle tone and metabolic process.
Yoga is helpful for fatty people to lose their weight also for abdominal fat.
For weight loss and be active, do yoga for at least 1 hr a day.
Yoga helps to improve from the hair of your head to the nails of your feet. I mean to say it helps all parts of your body. Even you have a breath problem, or if you can't walk, if you have pain in your back, in your legs, or headache anything else, Yoga is best for your health.

**The best time for yoga in the morning time before sunrise.