Dr. Puhl and her colleagues asked fat kids who was doing the bullying. It turned out that it was not just friends and classmates but also teachers and — for more than a third of the bullied — parents.

“If these kids are not safe at school or at home, where are they going to be supported?” Dr. Puhl asked.

The bullying problem is not limited to the United States. Dr. Puhl and her colleagues found the same situation in Canada, Australia and Iceland.

Women face harsher judgment than men, Dr. Puhl reports. The cutting remarks can begin when a woman’s body mass index is in the overweight range, while for men the shaming tends to start when they are obese. And women who are obese report more than three times as much shaming and discrimination as men of equal obesity.