These findings suggest the possibility that the stigma associated with being overweight,” the study concluded, “is more harmful than actually being overweight.”

And, in a cruel twist, one effect of weight bias is that it actually makes you eat more. The stress hormone cortisol—the one evolution designed to kick in when you’re being chased by a tiger or, it turns out, rejected for your looks—increases appetite, reduces the will to exercise and even improves the taste of food. Sam, echoing so many of the other people I spoke with, says that he drove straight to Jack in the Box last year after someone yelled, “Eat less!” at him across a parking lot.

There’s a grim caveman logic to our nastiness toward fat people. “We’re attuned to bodies that look different,” says Janet Tomiyama, a stigma researcher at UCLA. “In our evolutionary past, that might have meant disease risk and been seen as a threat to your tribe.” These biological breadcrumbs help explain why stigma begins so early. Kids as young as 3 describe their larger classmates with words like “mean,” “stupid” and “lazy.”

And yet, despite weight being the number one reason children are bullied at school, America’s institutions of public health continue to pursue policies perfectly designed to inflame the cruelty. TV and billboard campaigns still use slogans like “Too much screen time, too much kid” and “Being fat takes the fun out of being a kid.” Cat Pausé, a researcher at Massey University in New Zealand, spent months looking for a single public health campaign, worldwide, that attempted to reduce stigma against fat people and came up empty. In an incendiary case of good intentions gone bad, about a dozen states now send children home with “BMI report cards,” an intervention unlikely to have any effect on their weight but almost certain to increase bullying from the people closest to them.

This is not an abstract concern: Surveys of higher-weight adults find that their worst experiences of discrimination come from their own families. Erika, a health educator in Washington, can still recite the word her father used to describe her: “husky.” Her grandfather preferred “stocky.” Her mother never said anything about Erika’s body, but she didn't have to. She obsessed over her own, calling herself “enormous” despite being two sizes smaller than her daughter. By the time Erika was 11, she was sneaking into the woods behind her house and vomiting into the creek whenever social occasions made starving herself impossible.

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“There is no fate that cannot be surmounted by scorn.” -Albert Camus