Yoga is not the first thing that comes to mind when people are considering weight loss fitness strategies. It's not an aerobic exercise and aerobic exercise (even brisk walking) is considered best, as it burns the most calories and revs up the metabolism.
However successful weight loss is not all about the logical and physical aspect of diet and exercise. There is a mental (and even spiritual) element required to actually achieve the goal and to be able to change deeply entrenched daily habits.
If willpower or emotional issues are key aspects of your struggle with weight loss than a regular practice of yoga could be very helpful in providing you with a breakthrough in this regard. It can help you become much more aware of your subconscious mind and to instill a calmer and more joyful attitude to life.
Aside from this very important mental aspect of yoga, there is also the physiological benefit. Some of the yoga positions ('asanas') are particularly helpful in stimulating the thyroid gland. The thyroid is the key organ responsible for maintaining a healthy weight level.
The shoulderstand is the most effective yoga position for correcting thyroid imbalances. To see step-by-step instructions on how to do the shoulder-stand go to this page. I've read over twenty yoga books over the years and my personal favorite is "Yoga Self-Taught" by Andre Van Lysebeth. This book proposes a twenty minute routine of the best yoga positions. Their discussions of the health benefits of each of these asanas is outstanding.