The debate about whether or not doing yoga results in weight loss could go on and on. And to tell you the truth, I can see both sides of the argument.
But when it comes down to it, yes, yoga can aid in weight loss.
The science of weight loss is simple: you must burn more calories than you consume to lose weight. How many times have you heard that one liner? Like ANY other exercise program, to succeed at losing weight, you need to pair yoga with a healthy diet and lifestyle.
Please bear in mind there are many different types of yoga, some being much more vigorous (like power or vinyasa) than, say, yin or restorative. So obviously, if your intention is weight loss, and you need to burn maximum calories from your yoga practice, try a power yoga class. If it is heated you will drop water weight pretty instantly from all the sweat you will release.
It's true most types of yoga don't have anything near the calorie-burning power of aerobic exercise. However, in a yoga class, we connect our breath to movement; we are asked to notice the way certain poses and movements feel; we are asked to think about sliding our left hip forward while keeping our ribs tucked in and our spine long while we are balancing on one foot. The point I am getting at is that you start to recognize things that are happening in your body, you notice the way you feel physically and mentally. You are becoming mindful. Hence, this is the reason we call yoga a mind-body exercise.
The idea is that hopefully you can take this practice of mindfulness off the mat into your daily lives. You can have a mindful approach to eating. For instance, before you reach for a third slice of pizza, you stop, slow down, and ask yourself, "Am I still hungry?". Or, you have a choice at a restaurant between something you know is healthy and something that is clearly not, so you stop and think, "Which one will make me feel better afterwards?" I know that sounds so basic, but it's true that by practicing yoga, you start to become more aware of how you feel on the inside.
A negative attitude or outlook can cause weight gain, and can certainly hinder weight loss. In yoga, we talk about ahisma or nonviolence - to treat others with kindness and respect. You need to apply this philosophy in the way you treat yourself as well. It is important to have respect for what your body is capable of doing every single day, whether it is to hold a door open for a stranger, carry your groceries up 4 flights of stairs, or run a half-marathon.
Realize that your body enables you to live a good life, and does not just look "good" from the outside. Once you can grasp this notion, this ahisma towards yourself, you might even find yourself breathing easier, smiling more, and, ultimately even looking better from the inside, out.