"Why is my cat in better shape than I am? I go to the gym six days a week and torture myself there with fake skiing machines and iron maiden-like devices for hours on end. I eat all sorts of healthy food and pay attention to whether my fat is saturated or not and whether I am getting enough stuff like omega-3, whatever that is. And he just sleeps all day and eats whatever crap I feed him, plus bugs. Will I have to eat bugs? I don't want to."

I keep my cat ever so slightly fatter than I am at all times. She's a cat and doesn't care and I am a vain, vain human. It works.
It's because you're so smart.
Your cat probably doesn't drink, smoke and eat cheese.
OR your cat could be secretly bulimic, anorexic and taking laxatives. You may have a sorority cat.
Check the closet for bags of jars!
*(knocks on bathroom door)
"What? Oh, no - just a hairball. I'll be out in a minute!"
Has to be in better shape to live nine lives.
I've followed my cat's tips for years. I'm not sure if my longevity increased from drinking out of the toilet, but I usually have washrooms to myself.
I've also benefited from the flexibility exercises my cat taught me.
You need a big, ole catnip ball hung from the ceiling in your apartment. Yes, you do! Yes, you do! Who's an agile cat owner?! You are, you cute little furry thing!