New research shows that weight stigma—and not weight itself—has the biggest impact on mental health and healthy behaviors in the years after weight-loss surgery.

Researchers found that patients who had gone through weight-loss surgery tended to experience much less weight stigma, and that this reduction in weight stigma—but not lower BMI—was associated with healthier eating habits and better mental health. On the other hand, continuing to experience stigma after surgery was associated with higher risks of depression, anxiety, and disordered eating.

“We think of a lot of health issues for these patients as being a given,” says Larissa McGarrity, Ph.D., the first author on the study and a clinical psychologist in physical medicine and rehabilitation at University of Utah Health.

“But the cumulative effect of stigma and discrimination actually contributes to a large part of the physical and mental health problems that we disproportionately see for patients with obesity compared to the general population.”

The results are published in Health Psychology.

How weight-loss surgery affects quality of life

Metabolic bariatric surgery, commonly called weight-loss surgery, is the most effective evidence-based treatment for severe obesity. It reduces many health risks that are more common in people with obesity, including type 2 diabetes, heart disease, and all-cause mortality risk.

But many people expect weight-loss surgery to be a panacea for quality of life, and that’s not true. Some aspects of life, like social support and satisfaction with romantic relationships, tend to get worse.

People tend to experience significantly lower levels of weight stigma—shame, blame, and guilt around their body weight or shape—in the years following surgery, the researchers found in a survey of nearly 150 people.

McGarrity, who is also an associate professor in the Spencer Fox Eccles School of Medicine at the University of Utah, says that the change in experienced weight stigma was striking.

“The degree of change far exceeded clinically established norms in terms of what’s meaningful for a patient’s life and the impact they would notice,” she says.

This reduction in weight stigma was linked to notable improvements in both mental and physical health. Previous research has established that the chronic stress of weight stigma directly contributes to many of the health risks associated with obesity, and sure enough, people who experienced less stigma in the years following surgery had lower levels of anxiety and depression.

They were also less at risk for disordered eating, such as binge eating. And people who experienced less weight stigma were more likely to lose more weight and maintain the loss.

Lingering risks

Importantly, McGarrity notes, weight loss itself wasn’t associated with these positive changes to health. Change in BMI did not correlate with depression, anxiety, or dysregulated eating—implying that social factors, rather than innate biological ones, make a huge contribution to the mental and physical health of people with obesity.

And not every patient who went through weight loss surgery experienced a decrease in bias and stigma. For about 40% of patients, weight stigma continued to impact their quality of life, leading to increased risk of mental health concerns, disordered eating, and weight recurrence.

Since the survey targeted patients who were treated at U of U Health, future research will be needed to test whether the results hold true in broader populations.

The researchers say their work emphasizes the critical need to reduce weight stigma, both within health care settings and without. “The wide-ranging effects of weight stigma are one of the most important things I’m thinking about from both a research and clinical perspective,” McGarrity says.

“Weight loss is helpful for a whole lot of things, but that change in weight stigma may actually be the more powerful thing for mental health and quality of life over time.”