Why do some ppl poop more than others?

The amount of poop I poop every day is so much compared to the amount of food I’m eating. My partner eats at least 2x more than me and poops 3x less! This has always stumped me. She’s always like “how does such a little body have so much poop in it?!” Ahaha you’d think I was a 300 lbs man with the amount of poop I produce. But I’m a 100 lbs short girl.