Is it a bad idea to cut fat without gaining muscle?

I have a large constitution and I usually put on muscle quickly. However, I have limited access to weight training and I was wondering if I risk being underweight if I try to cut in order to get a lean stomach? My diet is good (no processed sugar) but when I exercise quite a bit I find my cheeks become sunken for a while and I'm thin everywhere when I just want to lose the belly flab! Good results so far but I'm beginning to look deprived despite getting a fair amount of fat/protein. I'll eventually hit the gym, but I'm just wondering for now...