Maybe try drinking Ensure with every meal. They have like 350 calories, But you have to get the one that says its to mantain a healthy weight, They are the ones with 350 calories, I think the others have 250. If you cant afford that you could try having a slimfast but make sure you drink one with every meal. My doctor also suggested carnation instant breakfast with every meal.
Hey, I am 4'11 about and 79 lbs with a bmi factor of about 15.3. The thing is, I'm a 14 year old female. I attract stares b/c I'm so thin, people think i have either cancer or im anorexic. I don't care about gaining fat, just to gain, like, 30 lbs so i can be normal.
I also think the BMI scale is very inaccurate. They don't consider muscle mass or a person's body frame type. Take into consideration that according to the BMI, body builders would be considered severely obese - when really they don't have much fat at all. They are solid muscle. In my opinion BMI is a joke.
When I was training for competitions I drank protein shakes every day (I forgot which brand - available at healthfood stores) They helped me keep my weight steady. I'm still very thin and people are constantly telling me to eat and that I need to gain weight (I'm so sick of hearing "Have a doughnut!").
If you're really worried, ask your doctor. He might be able to recommend some ways to gain weight safely.
some people are just naturally more thin than others. it may be that your digestive system is shorter and you have less time to digest your food.
but if you do want to gain wieght, they have wieght gain powder (kinda like a protien shake) at gnc. ive never tried it, but i think it would be worth a shot.