Have you count your BMI lately? Since I came to UK, my weight is still the same. It seems like I will never break through 50kg. I eat normal and have not been exercising a lot but still, my weight is around 50kg. When I went for my new patient check, the nurse told me that I am underweight. But when I told her that I have always been like this, she asked me not to worry since I am always like this.
If you google, you can easily find methods to lose weight but not to gain weight. All the weight gaining methods are about muscle building and such. Yeah, I did try to go to gym and drink protein but they did not work for me. A lot of my friends hope to be like me because they find it hard to lose weight. On the other hand, I sometimes, hope to be like them; the ability to control the weight.