More specifically, there are some asanas which aid slim people gain weight and look healthier. Note that yoga should be performed in loose clothes, on a mat and on an empty stomach. Ideally, before breakfast or in the evening at least two to three hours after lunch.
Surya Namaskar or The Sun Salute

This classic routine incorporates many poses from yoga into a minute long work out. If you do two Surya Namaskars a day your whole body gets a workout. It works especially for shoulders and chest. There are twelve positions. Spend five seconds on each. Start standing with hands folded in a namaskar. Reach up to the ceiling as far as you can and proceed to go down.

Touch your feet and assume a runner’s starting position by pushing your left leg far behind with knee bent. Now push your buttock up and form an arch with your body. Bring only your back down so that your stomach nearly touches the floor. Raise your head to the ceiling. Raise you buttock again and then resume the runner’s position. Bring both legs together, stand up but leave your hands touching your feet. Raise your hands towards the ceiling and resume the original namaskar.

Sarvangasana or the shoulder stand

Another great pose that helps you gain weight faster. Start by lying flat on a mat and raise your legs to a 45 degree. Your hands should remain outstretched until your legs are in the air. Now lift your arms and support your back with the fingers. Keep the thumbs on your rib cage and fingers as close to the shoulder blades as possible. It takes time to practise a pose to perfection so do not expect to perform the perfect asana the first few times. Straighten up your legs and point your feet to the ceiling as you straighten up your spine with your hands. Try to keep your elbows in a straight line as much as possible. Hold for about five seconds and return to the starting position slowly.