Less Weight is not good for health, it could cause many other problems, and spending life with low weight is also very tough for everyone, Here I am giving a wazifa to increase weight.

After the sunnah of the Fajr prayer, and before the fard of Fajr prayer, stay seated as you are and recite the Fatihah 41 times, and blow over yourself once you have done so.

Insha'Allah, Allah the Almighty will take your illness away, and grant you shifa' by increasing your weight.

 Do this as many times as possible, and until you notice an increase in your weight.