It's about story of growth

I always ask my brother to join me in every sport that I am interested. However, he doesn't want to join me, not even once.

I am thin but he is fat, erm not just fat, in fact, he is extremely fat....

He always claimed that he is fat so can't really do exercises.

For me, I always wonder, is it because what he said is real or because of he doesn't like to exercise and hence he becomes fat?

I think it's all about attitudes.