i guess u must 've seen advertisement on tv regarding weightgain that is use to gain weight but i dont think that it is really work for gaining weight , there are more ways to gain weight in a healty way , like try to balance your food daily , add some nutrious meal to your menu like milk or eggs , chocolate would be fine but not many, and avoid fat food or snack ,because snack or junk food can really make u lose appetite ,beside do some regular execises .