I am a 25 year old guy. I wants to gain weight. My height is 5 feet 7 inches n weight is 49 kg which is under normal. Sometimes I do not feel good as I am underweight. Please advice me some way to gain weight without any side effect.

You really should talk to a doctor about this.

Whenever you decide to drastically change your weight it's best to go to your doctor, have a physical, rule out any abnormalities that may be the cause of your weight.

Your doctor can recommend a safe diet and exercise program.

Good luck.