Wei Bao, MD, PhD Assistant Professor, Epidemiology College of Public Health University of Iowa

Bariatric Surgery: Even Modest Pre-Op Weight Loss Linked to Decreased 30-Day Mortality

MedicalResearch.com Interview with:

Wei Bao, MD, PhD Assistant Professor, Epidemiology College of Public Health University of Iowa

Dr. Wei Bao

Wei Bao, MD, PhD
Assistant Professor
Department of Epidemiology,
College of Public Health,
University of Iowa,
Iowa City, IA 52242 and

Yangbo Sun  MD, PhD Department of Epidemiology University of Iowa

Dr. Yangbo Sun

Dr. Yangbo Sun, PhD

(Former postdoc research scholar at University of Iowa)
Tenure-track Assistant Professor
The University of Tennessee Health Science Center.


MedicalResearch.com: What is the background for this study?

Response: Obesity is a rising epidemic in the United States and worldwide. Bariatric surgery has been shown to be the most effective and durable treatment for clinically morbid obesity which is difficult to reverse through traditional approaches such as lifestyle intervention. There has been long-standing uncertainty and debate regarding the value of pre-operative weight loss as a requirement for bariatric surgery. Meanwhile, one of the major indicators for surgery outcomes is 30-day mortality after surgery, which is especially important for bariatric surgery because the vast majority of the patients undergoing bariatric surgery are voluntary and if the surgery were not performed, they are not supposed to die in short term.

So far, the association of pre-operative weight loss with 30-day mortality after bariatric surgery remains unclear. Therefore, in this study, we examined the associations of pre-operative BMI and weight loss with 30-day mortality following bariatric surgery using a large database among ~500,000 patients who underwent bariatric surgery in the United States and Canada.

MedicalResearch.com: What are the main findings? 

Response: In a large cohort study of 480,075 patients who underwent bariatric surgery during 2015-2017, we found that weight loss prior to bariatric surgery, even a modest weight loss, was associated with lower risk of 30-day mortality following bariatric surgery. Compared with patients with no pre-operative weight loss, patients with weight loss of <5%, 5-9.9%, and ≥10.0% had 24%, 31%, and 42% lower risk of 30-day mortality, respectively.

MedicalResearch.com: What should readers take away from your report? 

Response: Our study revealed that pre-operative weight loss, even at a moderate degree (<5% weight loss), was associated with lower risk of 30-day mortality following bariatric surgery. 

MedicalResearch.com: What recommendations do you have for future research as a result of this work?

Response: First, further investigation is needed to replicate our findings in other settings or populations. Second, whether the observed association in this study varies by different weight loss approaches (e.g., diet, exercise, pharmaceutical interventions) warrants further investigation. The ultimate goal is to inform future updates of clinical guidelines regarding bariatric surgery. 

We do not have any disclosure. 


Sun Y, Liu B, Smith JK, et al. Association of Preoperative Body Weight and Weight Loss With Risk of Death After Bariatric Surgery. JAMA Netw Open. 2020;3(5):e204803. doi:10.1001/jamanetworkopen.2020.4803



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Last Updated on May 16, 2020 by Marie Benz MD FAAD