Sport Question about Ectomorphs

[amp89]

I just have a question that has been bothering me, and I was hoping someone could answer it. People come on to these forums all the time saying that they are trying to gain weight, and that they have add 1000+ cals a day and have not gained any weight. Usually the advice given to these people is to eat even more. I was curious as to why these people are not losing weight when they are not eating the extra 1000 calories? The only reason I can think of is that their bodies are compensating for those extra calories by using up extra energy, which is connected to the set point theory. Anyway, just wondering, doesn't have anything to do with me, just want to learn.