If you have a difficult time gaining weight of any kind (fat or muscle) then you most likely have a fast metabolism. That simply means that your body burns calories at a faster than normal rate. You must take this into account whenever you are considering a particular diet or training program. Is it geared towards someone with your metabolism and goal?
Now as you know, there are many ways to train. Hundreds, thousands even. Some work and some do not, but for the specific goal of gaining weight, there are a few UNIVERSAL things that all skinny guys must do ,.
WHY CAN'T YOU GAIN WEIGHT?
WHY CAN'T YOU GAIN WEIGHT?
Though there may be many reasons why you may be thin, the most apparent reason is because of your genetics. If your parents are naturally thin or have a small body frame, then you will most likely have the same small body type.
To some degree, your size can also be controlled by your metabolism ,