If you’re one of the nearly 40 percent of Americans who are obese, you don’t need anyone to explain the associated stigma; you’ve probably experienced it in some form or another — jokes about your weight, teasing, bullying, employment discrimination (which is legal in 49 states), prejudice and unfair treatment. This kind of stigmatization doesn’t just create hurt feelings, it can harm your health. The research suggests that reducing stigma against obesity could give overweight people a health boost — even if they never shed a single pound.

Stigma can harm health in many ways. It can discourage people from taking part in healthy behaviors like exercise, which improves health regardless of whether it leads to weight loss, and it can erode mental health. One large study found that perceived weight discrimination is associated with a host of psychiatric disorders, including depression and anxiety, and another found that weight discrimination is associated with a shorter life, even after researchers controlled for body mass index in both cases. Even perceiving yourself as overweight when you aren’t is linked to poorer health down the line.

And stigma creates a vicious cycle. People who report experiencing weight stigma are more likely to gain weight in the future and attain a BMI categorized as “obese.” Behavior likely contributes to this trend: When people get stressed out, they tend to soothe themselves with comfort food and are more likely to fail at attempts to self-regulate — meaning that, among other things, they are less likely to stick to a healthful diet. But there is also some evidence that physiological factors contribute to weight gain among people who experience stigma. A. Janet Tomiyama, a psychology professor at UCLA, is studying the relationship between weight stigma and cortisol, a hormone that responds strongly to stress. Cortisol signals the body to store more fat, especially in the abdominal area, and it increases appetite and makes the brain’s reward centers more sensitive in response to treats like sugar and fatty foods. And that’s what makes weight stigma doubly pernicious, she said. In addition to the pain and stress it causes, “experiencing it makes the original condition more exacerbated.”

Weight loss surgery is a highly effective way to lose a significant amount of weight and to treat Type 2 diabetes, but stigma can discourage people from getting it. One study found that people who saw a photograph of a woman before and after significant weight loss thought she was lazier, less competent and less responsible when they were told she had surgery compared to when they were told she lost the weight through diet and exercise. A recent national survey published in JAMA Surgery found that almost half of respondents thought most people who had the surgery did so for cosmetic reasons. And more than 39 percent thought people who had the surgery chose “the easy way out,”even though weight-loss surgery requires a lot of preparation and long-term effort. The survey results also support — though can’t confirm — the hypothesis that stigma surrounding the surgery prevents some people from getting it, even if they could benefit from it: The demographic groups more likely to have those negative attitudes are also the ones least likely to get the surgery. “It puts people who qualify for surgery between a rock and a hard place,” said Patrick Dolan, an author of the JAMA Surgery study and a surgical resident at New York-Presbyterian Hospital, Weill Cornell Medical Center.

The core belief underlying weight stigma is that people are personally responsible for their body weight, said Rebecca Puhl, a professor and deputy director for the Rudd Center for Food Policy & Obesity at the University of Connecticut. From that follows the idea that weight loss is entirely within an obese person’s control; it just requires the willpower to eat less and exercise more. But that attitude is based on “a huge oversimplification” of what we know about how our bodies regulate weight,” said Puhl. Studies show that it is physiologically very difficult to lose weight and keep it off over the long term, especially once someone has become obese. It’s not a simple matter of calories in, calories out. And the easy availability of unhealthful foods, the prevalence of activities that encourage being sedentary and other “obesogenic” factors have created a perfect environment to promote obesity, said Puhl. Sure, individual behavior does play a role in weight loss and maintenance, but it’s certainly not the only — or necessarily the most important — factor. Yet the myth that overweight people are simply lazy and unmotivated persists.

You’d think that as with most other forms of prejudice, family and friends, at least, would serve as a bulwark against the cruel outside world. But research shows that family members are one of the most frequent sources of reported weight bias. “We find that the people who are closest to us are also the ones more likely to stigmatize us,” said Tomiyama. That can be particularly damaging.

We usually expect health and medical professionals to have compassion for the people they care for, but studies have demonstrated weight bias among trainers and nutritionists, medical students, nurses and physicians. The consequences go beyond hurt feelings. Tomiyama and colleagues have noted that bias among health care workers “has direct and observable consequences for the quality and nature of services provided to those with obesity,” which could harm patients’ health. They cite studies showing physicians may spend less time with and engage in less health education with patients who have higher BMIs. Feeling this negativity, patients with higher BMIs say they avoid seeking health care. Some people have argued that stigma is desirable because it puts social pressure on people with obesity to lose weight. But the science suggests just the opposite. If the public health goal is to curb obesity and improve health, stigma just makes everything worse.