Weight-loss surgery has improved the health of millions of people. Its biggest benefit, however, may not be the loss of weight itself, but the profound relief patients can feel as the stigma of being overweight is lifted.

Weight-loss or bariatric surgery reduces many health risks common among people who are overweight, including type 2 diabetes and heart disease, as well as a higher risk of all-cause mortality.

“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.”

The surgery produced enormous relief in the years following surgery among those patients who experienced significantly lower levels of weight stigma — the shame, blame and guilt they felt because of their body weight or shape. It was this, not their lower BMIs, that seemed to inspire them to develop to healthier eating habits and improved their mental health, a recent survey of weight-loss surgery patients found.

“The degree of change [patients reported after the surgery] far exceeded clinically established norms in terms of what's meaningful for a patient's life and the impact they would notice,” explained the first author on the study, Larissa McGarrity.

On the other hand, patients who continued to experience stigma after surgery had a higher risk of depression, anxiety and disordered eating.

The results come from a survey of 150 weight-loss surgery patients at University of Utah Health. University of Utah researchers asked patients about their physical and mental health. Their answers offer a view of what many bariatric patients struggle with beyond the numbers on a scale.

“[T]he 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,” McGarrity, a clinical psychologist in physical medicine and rehabilitation at University of Utah Health, said.

Previous research had shown that the chronic stress of weight stigma directly contributes to many of the health risks associated with obesity. Sure enough, patients in the study who said they experienced less weight stigma in the years following surgery also reported notable improvements in both mental and physical health.

Relieved of the stigma of being obese or severely overweight, they had lower levels of anxiety and depression and were less at risk for disordered eating, such as binge eating. They were also more likely to lose more weight and maintain the loss.

Patients who said they experienced less weight stigma in the years following surgery reported improvements in both mental and physical health and were more likely to maintain their weight loss.

The results made it clear that weight loss itself wasn't responsible for these positive changes. A reduction in BMI did not correlate with depression, anxiety or dysregulated eating. Rather, it appeared that social factors, instead of innate biological ones, made a huge contribution to the mental and physical health of people with obesity.

It's important to note that not every weight-loss surgery patient experienced less bias and stigma. And sometimes patients expect weight-loss surgery to be a cure-all for their quality of life, but that's not necessarily true. For some, certain aspects of life, like social support and satisfaction with romantic relationships, can deteriorate post-surgery.

For about 40 percent of patients, weight stigma continued to impact their quality of life, leading to increased risk of mental health concerns, disordered eating and recurrent weight gain.

The study shows how great the need to reduce weight stigma is, both within health care settings and outside them, the researchers say. “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,” McGarrity said.

The study is published in Health Psychology.