More than 3.2 million children are stigmatized and bullied every year, and one of the main reasons is they're "fat." Even teachers belittle the problem, with one in four seeing nothing wrong and, according to DoSomething.org, intervene only 4 percent of the time.

"We've seen that weight bias has worsened as obesity rates have risen," Rebecca Puhl, a professor of human development and family studies at the University of Connecticut told symptom.com. "Our research shows that weight-based bullying is the most common reason that youth are bullied at school."

Bullying must be stopped, say experts, not only for a child's current well-being, but for their future health. A study published in the American Journal of Psychiatry found that adults who had been bullied as children had an increased risk of depression, anxiety disorders, and suicidal thoughts than their peers, as well as fewer social relationships.

Even though bullying has drawn national attention, not enough focus has been given to weight-bullying, since most state laws that address bullying include issues such as race, religion, and sexual orientation, but omit obesity.

"It is actually legal to discriminate on the basis of weight, and that sends a message that bias, unfair treatment or bullying of overweight children is tolerable," Puhl told the New York Times.

As more people have become obese, taking personal responsibility for weight gain has gained prominence. "There is a perception that these youth are somehow to blame for their weight and in some way deserve this treatment," Puhl said.

"There’s also a widespread misperception that stigma may not be such a bad thing, and that maybe criticism will get people motivated to lose weight," she told the New York Times, but added that studies have shown that the tactic doesn't work.

Recent research published in the International Journal of Obesity studied anti-fat attitudes in four countries with similar rates of childhood and adult obesity — the United States, Australia, Canada, and Iceland. Approximately 69 percent of the 2,866 adults surveyed found bullying because of weight to be a "serious" or "very serious" problem, and about 75 percent said schools should take steps to address the problem.

However, educators are already aware of the problem, with a study by the National Education Association reporting that 23 percent of teachers considered bullying because of weight being more common than bullying based on sexual orientation, physical disability, and other reasons.

A 2011 report by the Centers for Disease Control found that even doctors — one in three — held weight biases. The report also found that some parents were biased against their obese children, and almost half of overweight girls were teased by their families.

"The politically correct movement doesn’t seem to have touched body weight," Deborah Carr, chair of the sociology department at Rutgers University, told the New York Times. "Weight stigma is the most acute among upper middle class educated people, which is the population that cherishes the lean physique the most."

The public health message most often heard ignores that some genetic differences make it harder for some people to control their weight than others, and that proper weight can be achieved by eating less and exercising. Health experts must maintain a delicate balance between "wanting someone to have a healthy body image and feel good about themselves at any size — and wanting them to watch their weight," said Carr.