Impact of Bariatric Surgery on Health Depends on Type of Surgery, Patient Characteristics

PASADENA, Calif. – The impact of bariatric surgery on risk factors for cardiovascular disease depends on a variety of factors, including the type of surgery, sex of the patient, ethnic background, and pre-surgery body mass index, according to a Kaiser Permanente study published today in Annals of Surgery. 

Researchers examined the electronic health records of more than 4,000 Kaiser Permanente patients in Southern California who had bariatric surgery for weight loss between 2009 and 2011 to determine what factors led to remission – or reduction – of metabolic syndrome after surgery. Metabolic syndrome is a group of health conditions that increase a person’s risk of coronary artery disease, stroke and type 2 diabetes. Patients were studied for up to two years after their bariatric surgery to determine if their metabolic syndrome improved. 

Researchers found that non-Hispanic black and Hispanic patients were less likely than non-Hispanic white patients to experience metabolic syndrome remission. These differences in remission were not a result of greater weight loss during the follow-up period; racial and ethnic differences persisted even when researchers controlled for the rate of weight loss.

Although we do not know the reasons for the racial and ethnic differences we saw, one explanation could be that the black and Hispanic patients had surgery when they are much heavier and sicker than the non-Hispanic white patients, said study lead author, Karen J. Coleman, PhD, of the Kaiser Permanente Department of Research & Evaluation in Pasadena, Calif. Our study highlights that surgery may be an important intervention tool for people earlier in their weight gain trajectory. The heavier they become, the less likely that surgery will be successful at reducing these cardiovascular disease risk factors. 

Researchers also found:

·       Women were more likely than men to experience remission,

·       Patients who were heavier at the time of their surgery were less likely to experience remission than those who were lighter, and

·       Patients who received the gastric sleeve, which is the fastest growing new bariatric procedure, were less likely to experience metabolic syndrome remission than patients who had a traditional gastric bypass. 

According to the American Heart Association, 35 percent of Americans are affected by metabolic syndrome. People with metabolic syndrome have a two-fold risk for heart attack or stroke, and a five-fold increased risk for developing diabetes compared to individuals who do not have the condition. The AHA predicts that the cost to treat Americans with heart failure will increase to $53 billion annually by 2030. 

In the majority of patients, bariatric surgery may result in the remission of many cardiovascular disease risk factors, which could prevent those patients from experiencing more serious health conditions, such as heart attack and stroke, Coleman said. The benefits of bariatric surgery are different for men and women and different racial/ethnic groups. This study highlights the importance of designing post-operative care models to address the unique challenges different genders and ethnic/racial groups face following bariatric surgery.

With more than 4,000 patients, this study had one of the largest sample sizes for bariatric surgery procedures, and included follow-up information on weight, blood pressure, quality of life, and laboratory and pharmacy data on the majority of patients in the sample. Previous studies in the area had sample sizes of 50 to 200 patients, most of whom were non-Hispanic white. Nearly half (49 percent) of the Kaiser Permanente study’s sample were either Hispanic or non-Hispanic black, providing a unique opportunity to study the effect of bariatric surgery on metabolic syndrome in different racial/ethnic groups. In addition, this is one of the largest studies to examine the impact of the fastest growing bariatric procedure, the gastric sleeve, on patient health outcomes. 

This study is part of Kaiser Permanente’s ongoing efforts to understand the impacts of obesity and obesity-related conditions, such as type-2 diabetes, on a person’s health. A Kaiser Permanente study published last year found almost half of adults with type 2 diabetes report acute and chronic pain, and close to one quarter report neuropathy, fatigue, depression, sleep disturbance, and physical or emotional disability. Another Kaiser Permanente study published in early 2012 found electronic health records and embedded tools can alert and direct pediatricians so they can better manage their young patients’ weight. 

Kaiser Permanente can conduct transformational health research in part because it has the largest private patient-centered electronic health system in the world. The organization’s electronic health record system, Kaiser Permanente HealthConnect®, securely connects 9.1 million patients to 1,700 physicians in 611 medical offices and 37 hospitals. It also connects Kaiser Permanente’s research scientists to one of the most extensive collections of longitudinal medical data available, facilitating studies and important medical discoveries that shape the future of health and care delivery for patients and the medical community. 

Study authors include Karen J. Coleman, PhD; Yii-Chieh Huang, MS; Corinna Koebnick, PhD; Kristi Reynolds, PhD, MPH; Anny H. Xiang, PhD; and Mary Helen Black, PhD, of the Kaiser Permanente Department of Research & Evaluation; and Sami Alskaf, MD, of the Kaiser Permanente Panorama City (Calif.) Medical Center. 

About the Kaiser Permanente Department of Research & Evaluation

The Department of Research & Evaluation conducts high-quality, innovative research into disease etiology, prevention, treatment and care delivery. Investigators conduct epidemiology, health sciences and behavioral research as well as clinical trials. Areas of interest include diabetes and obesity, cancer, HIV/AIDS, cardiovascular disease, aging and cognition, pregnancy outcomes, women’s and children’s health, quality and safety, and pharmacoepidemiology. Located in Pasadena, Calif., the department focuses on translating research to practice quickly to benefit the health and lives of Kaiser Permanente Southern California members and the general population. Visit

About Kaiser Permanente

Kaiser Permanente is committed to helping shape the future of health care. We are recognized as one of America’s leading health care providers and not-for-profit health plans. Founded in 1945, our mission is to provide high-quality, affordable health care services to improve the health of our members and the communities we serve. We currently serve more than 9.1 million members in nine states and the District of Columbia. Care for members and patients is focused on their total health and guided by their personal physicians, specialists and team of caregivers. Our expert and caring medical teams are empowered and supported by industry-leading technology advances and tools for health promotion, disease prevention, state-of-the art care delivery and world-class chronic disease management. Kaiser Permanente is dedicated to care innovations, clinical research, health education and the support of community health. For more information, go to