Once upon a time, I could eat everything in sight, and not gain a pound. When I graduated from High School, and on up through my twenties, my weight was pretty consistently 150-155 lbs. I wore jeans with a 32" waist. But then I hit my thirties, and something happened. My metabolism slowed down. That, combined with a sedentary occupation that largely involves sitting at a computer keyboard, resulted in a gradual expansion of my waistline. I was losing the Battle of the Bulge.
In short, I got fat.
Not ponderously fat, but noticeably overweight. It was easy enough for me to laugh away the fact with wisecracks such as "Sure, I'm in shape. After all, pear is a shape." Hey, I had become an oblate spheroid, just like the earth.