I consider myself a guy who is in good shape but I've been working full-time for the past 4 years now sitting inside a cubicle and even though I try to eat healthy, it's hard to avoid the gain in the belly area. It's the only place where I'm noticing fat. I focus on ab workouts at the gym and I might start running now. Considering that I put a lot of effort in trying to stay in shape and eat healthy, I can only imagine how drastic the "average" person would notice belly fat with age