Like everything else foreigners claim about "Americans" when they don't actually know what they're talking about, you're probably confusing poor people with the whole country. Middle class and up are normal to fit, with a few fat people, but mostly normal weight to fit. Our poor people have most of the obesity, commit most of the crime, are bad drivers who smash into things and still drive around in a car with the door caved in or bumper hanging off, most of them have pit bulls, can't seem to hold down a job for any extended period, and they're mostly single moms and deadbeat dads who keep having like 9 kids with several people when they couldn't even afford the first one.