Yoga helps in weight management. Before i get to the answer to how, i would like to put forth the possible effect of yoga in our life along with factors that contribute weight gain.
Weight gain or having a heavy body can be due to an unhealthy lifestyle which involves eating the wrong kind of food, improper food timings which in turn has an effect on your sleep cycle etc. Along with this, weight gain is also from improper functioning of internal organs and systems. This results in poor metabolism and heavy weight. If we have to get to the bottom of this, then its mainly because of the disconnect with the body which doesn't allow you to function at your optimum and that forms the base for weight gain.
Practicing yoga brings about a change in your mindset. You learn to talk to and reconnect with your body. You changes the way you approach life, your body, mind and eating habits. You learn to appreciate how much the body has been working for you , supporting you and Yoga shows you how to appreciate your body for all the amazing things that it does and can do for you. This change in your body-mind is a more effective tool in weight loss than just stressfully depriving yourself of junk or pushing yourself beyond your limits in exercises. You become more aware of your intake and be mindful of your habits.
Although i won't be able pinpoint a set of asanas that have to be practiced for weight loss, deep breathing and other breathing techniques in yoga form its base to cleanse, balance , massage and rejuvenate internal organs and their functions are very helpful. Yoga postures with proper breathing help in increasing the metabolism and that in turn helps in digestion and regularising the intake of food. This helps in working from within and be friends with your body rather than fight it.
Working on the cardio vascular muscles in tune with the breath helps in increasing the lung capacity, heart rate, strengthen your core and stamina which will also contribute to reducing the weight.
Working on your flexibility also contributes to being fit. Yoga involves twisting the body, forward and backward bends, inversions and other poses that help in opening up the otherwise unused muscles and thereby facilitate weight loss.