I started a program of weight training when I was 34. I weighed 125 pounds when I started out (I'm 5' 9" tall), so the task for me was to gain muscle rather than to lose fat. It has pretty much always been that way, though there was a time when some of the bulk that I had put on was visible fat -- a slight pooling about the middle. I seem to have reached a stable weight around 160 pounds. I think it took me two or three years to get to that point, and I have stayed there, apart from a couple of periods during which I did not exercise and lost a lot of weight. I go to the gym about four times a week, and do 20 minutes of running on an elliptical trainer and 30 minutes of training with weights.
There is one guy at the gym who looks about the same size and weight as I am but with a much more defined musculature, as well as greater bulk in the chest and shoulders. My first thought upon seeing him was "I wish I could look like that." But from noting the times when I have seen him there, I have figured out that he works out from about 5 a.m. to 7:30 a.m., five days a week! I like the way he looks, but if it takes that kind of effort, it's not worth it to me.