My son is 21 yrs old & only weighs 103 lbs, what cam he take or do to gain some. he eats normal & hardly drinks soda. he is a smoker also.

Quit smoking: He ought to quit smoking now. He may be underweight due to use of tobacco and he is damaging his health by his smoking. No good can come from use of tobacco in any form.

Hw wll do U know him: Does he vomits his food? Does he have diarrhea? Has he consulted his family physician? Some people grow naturally thin! Others may have an unsuspected disorder.