Epidemiology and Trends of Obesity and Bariatric Surgery in Korea
Article information
Abstract
The prevalence of obesity in Korea has steadily increased over the past decade, reaching 38.4% in 2021. Notably, the rate of class II–III obesity, defined as a body mass index (BMI) of 30 kg/m2 or higher, exceeded 7% in the same year. Since January 2019, the National Health Insurance Service (NHIS) has provided coverage for bariatric surgery (BS) for eligible patients. Coverage is available for individuals with a BMI of 35 kg/m2 or higher, or those with a BMI of 30 kg/m2 or higher who also have obesity-related comorbidities. Additionally, partial reimbursement is offered for BS in patients with type 2 diabetes mellitus who have BMI values between 27.5 and 30 kg/m2. From 2019 to 2022, the NHIS recorded 9,080 BS procedures, with sleeve gastrectomy being the most commonly performed. The average percentage of weight loss 198±99.7 days post-surgery was 17.9%, with 80.0% of patients losing more than 10% of their body weight. This article presents the trends in obesity and BS in Korea.
INTRODUCTION
Obesity, characterized by excessive fat accumulation, has been implicated as a contributing factor to the morbidity and mortality associated with major chronic diseases, including type 2 diabetes mellitus (T2DM), dyslipidemia, hypertension, fatty liver, and cardiovascular diseases [1]. The prevalence of obesity has increased substantially worldwide, and developing effective treatment strategies is crucial for reducing the disease burden and premature mortality linked to obesity-related comorbidities. Bariatric surgery (BS) for morbid obesity is an effective treatment that leads to the improvement and remission of many obesity-related comorbidities [2]. Since 2019, the National Health Insurance Service (NHIS) of Korea has extended coverage for BS to individuals with morbid obesity. This review presents recent trends in the prevalence of obesity among adults in Korea, based on the 2023 Obesity Fact Sheet [3], and discusses the trends and outcomes of BS in Korea, utilizing data from the Korean National Health Information Database (NHID).
EPIDEMIOLOGY OF OBESITY IN KOREA
Obesity is defined by the Asia-Pacific criteria of the World Health Organization as a body mass index (BMI) of 25 kg/m2 or higher [4]. The Korean Society for the Study of Obesity (KSSO) categorizes overweight (pre-obesity) as a BMI of 23 kg/m2 or higher and obesity as a BMI of 25 kg/m2 or higher, based on a marked increase in obesity-related comorbidities (Table 1) [5]. A cohort study involving 773,915 Korean men and women, aged 30 to 59, followed for 8 to 10 years, found that the population with a BMI of 25 kg/m2 or higher is rapidly increasing and faces a significant risk for metabolic diseases [6]. The study also indicated a steadily increasing risk for hypertension and hypercholesterolemia starting at a BMI of 18.5, and for T2DM beginning at a BMI of 21 to 22 kg/m2 [6]. The 2017 Obesity Fact Sheet in Korea reported that the risk of T2DM, hypertension, and dyslipidemia increases linearly with BMI in the range of 23 to 25 kg/m2 [7]. Notably, the risks for T2DM, hypertension, and dyslipidemia rise significantly when BMI exceeds 25 kg/m2, the threshold for obesity in Korea. According to the 2021 Obesity Fact Sheet in Korea, the relative risk of T2DM, myocardial infarction, and ischemic stroke in individuals with obesity (defined as a BMI of 25 or higher) is 2.6, 1.2, and 1.1 times higher, respectively, than in those without obesity [8]. These findings highlight that Koreans face a higher risk of obesity-related diseases at relatively lower BMIs than Western populations [6-8]. A waist circumference of 90 cm or more in men and 85 cm or more in women is defined as abdominal obesity, which is also associated with an increased risk of obesity-related comorbidities [5].
The prevalence of obesity in Korea has steadily increased over the past 10 years since 2012 [3]. In 2012, the overall population’s obesity rate was 30.2%, rising to 38.4% by 2021 (Fig. 1A) [3]. Notably, the prevalence of class III obesity, defined as a BMI of 35 kg/m2 or higher, has nearly tripled from 0.38% in 2012 to 1.09% in 2021 (Fig. 1B). Additionally, the prevalence of class II obesity, defined as a BMI of 30 to 34.9 kg/m2, has increased 1.6-fold, from 3.6% in 2012 to 5.9% in 2021. The prevalence of class II–III obesity, defined as a BMI of 30 kg/m2 or higher, surpassed 7% in 2021 [3]. This increase was more pronounced in men than in women (Fig. 1C). The highest prevalence of class III obesity was observed in men in their 20s (2.6%) and 30s (2.6%), and in women in their 30s (1.59%) [3]. The 2023 Obesity Fact Sheet [3] highlights a significant increase in the prevalence of class II and III obesity, particularly among young adults aged 20 to 39 years. Millennials, born in the mid-1980s to early 2000s, exhibited a significantly higher incidence of obesity than the previous generation. This demographic also showed relatively higher rates of problematic smartphone use, which is associated with a sedentary lifestyle and may contribute to the rising prevalence of obesity [3].
TREATMENT GUIDELINES FOR BARIATRIC SURGERY IN KOREA
According to the obesity management guidelines issued by the KSSO, BS should be considered for Korean adults with a BMI of 35 kg/m2 or higher, or a BMI of 30 kg/m2 or higher accompanied by obesity-related comorbidities, particularly if they have not achieved weight loss through nonsurgical treatments [9]. BS is also advised for individuals with T2DM who have a BMI of 27.5 kg/m2 or higher and whose blood sugar levels remain uncontrolled with nonsurgical treatments (Table 2). It is recommended to select from established procedures known for their effectiveness and safety, such as sleeve gastrectomy (SG), Roux-en-Y gastric bypass (RYGB), adjustable gastric banding, and biliopancreatic diversion/duodenal switch, considering the individual’s specific condition [9]. The Korean Diabetes Association (KDA) suggests that BS may be considered for adults with T2DM and obesity (BMI ≥30 kg/m2) who have not been successful in losing weight or achieving glycemic control through nonsurgical treatments [10]. The KDA has not endorsed a lower BMI cutoff of 27.5 kg/m2 due to the limited data on long-term outcomes in Koreans with a BMI below 30 kg/m2 [10,11]. In Korea, the NHIS has provided coverage for BS since January 2019. Individuals with a BMI of 35 kg/m2 or higher, or a BMI of 30 kg/m2 or higher with obesity-related comorbidities, are eligible for this coverage. Partial reimbursement is available for BS in patients with T2DM who have BMI values between 27.5 and 30 kg/m2. In Japan, BS is recommended for obese patients with a BMI of 35 kg/m2 or higher primarily for weight loss, and for those with a BMI of 32 kg/m2 or higher who have diabetes mellitus (DM) or at least two other nondiabetic obesity-related health conditions [12]. The guidelines for BMI eligibility for BS vary among Asian countries, leading to differences in the practice of BS from one country to another.
Deciding whether to perform BS in older patients can be challenging. Some research suggests that age does not necessarily increase the risk of complications following BS [13]. Therefore, if the potential postoperative complications do not outweigh the benefits in reducing obesity-related disability, surgical treatment may be considered for older adults with obesity.
TRENDS OF BARIATRIC SURGERY IN KOREA
Retrospective data from patients who underwent BS were analyzed using the NHID collected by the NHIS in Korea, spanning from January 2019 to December 2022. This study received approval from the Institutional Review Board of Seoul National University Hospital (No. E-2305-152-1435). Since anonymized and de-identified information was utilized for the analyses, informed consent was not required. Detailed codes related to these BS procedures can be found in Supplemental Table S1. T2DM was defined by the presence of an International Classification of Disease, 10th Revision (ICD-10) code (E11–E14) along with a prescription for antidiabetic medications. Hypertension was identified by the presence of an ICD-10 code (I10–I13) and a prescription for antihypertensive medications. Dyslipidemia was characterized by the presence of an ICD-10 code (E78) and a prescription for antihyperlipidemic medications. The annual number of BS procedures either slightly increased or remained stable, rising from 2,368 in 2019 to 2,405 in 2022. Between 2019 and 2022, a total of 9,080 BS cases were reported to the Korea NHIS (Fig. 2A). Among these cases, 74.1% were women and 25.9% were men, with women undergoing BS approximately three times more frequently than men (Fig. 2A). The average age of individuals undergoing BS during this period was 37.5 years, with the most common age group being 20 to 39 years old, accounting for 59.6% of the cases (Fig. 2B). Additionally, 30.0% of the individuals who underwent BS also had T2DM, 38.9% had comorbid hypertension, and 34.3% had dyslipidemia.
(A) Annual number of bariatric surgery cases in Korea from 2019 to 2022 and sex distribution of cases: 74.1% of bariatric surgery patients were women, and women underwent bariatric surgery about three times more often than men. (B) Age distribution of bariatric surgery in Korea: the most common age group receiving a bariatric surgery was 20 to 39 years old (59.6%).
In terms of the type of operation, SG was the most commonly performed procedure, accounting for 75.1% of all cases (Fig. 3A). RYGB was the next most frequent, at 11.7%, followed by duodenal switch, which was performed in 5.0% of cases. Among patients with T2DM, SG and RYGB accounted for 58.7% and 23.1% of procedures, respectively. In contrast, in patients without DM, the proportions were 82.2% for SG and 6.7% for RYGB (Fig. 3B).
(A) Frequency of bariatric surgery procedures in Korea from 2019 to 2022: sleeve gastrectomy was the most commonly performed procedure (75.1%). (B) Frequency of bariatric surgery procedures in Korea by the presence of type 2 diabetes mellitus: Roux-en-Y gastric bypass and duodenal switch, which are procedures with a malabsorptive component, were performed at a higher rate in patients with type 2 diabetes mellitus (left panel) than in patients without type 2 diabetes mellitus (right panel).
According to a nationwide survey on BS in Korea from 2003 to 2013, the annual number of BS cases reached 1,578 in 2012 and 1,686 in 2013 [14]. The most frequently performed procedure was the adjustable gastric band, accounting for 67.2% of cases, followed by SG at 14.2%, and RYGB at 12.7% [14]. Since 2019, the annual number of BS cases has surpassed 2,000, and there has been a shift in the prevalence of procedures, with SG now being the most commonly performed.
THE EFFECT OF BARIATRIC SURGERY IN KOREA
The Korea NHID include all claims data and health screening information, complete with detailed lifestyle questionnaires and laboratory results. Enrollees in the NHIS are advised to undergo a standardized medical examination at least once every 2 years [15]. These regular health examinations consist of anthropometric measurements, blood pressure assessment, evaluations of alcohol and smoking status, and physical activity, along with laboratory tests conducted after overnight fasting to measure serum glucose.
A total of 843 subjects underwent health examinations before and after BS to assess changes associated with the procedure (Table 3). The median interval between the preoperative evaluation and the day of BS was 195.5±99.7 days, while the median time from the day of BS to the postoperative evaluation was 198.8±99.7 days. Weight change was calculated using the formula: [(weight after BS–weight before BS)/weight before BS)]× 100, resulting in a percentage of body weight loss. The average weight loss from pre- to post-BS was –17.9%, with 80.0% of participants losing 10% or more of their body weight. The change in BMI closely mirrored the weight loss percentage, with men experiencing greater reductions in both weight and BMI compared to women. Waist circumference decreased by 13.6% following surgery. Fasting blood glucose levels also showed improvement, decreasing by approximately 20 mg/dL from a preoperative average of 118.0±44.4 mg/dL to a postoperative average of 96.8±19.6 mg/dL. Additionally, both systolic and diastolic blood pressure levels decreased postoperatively. We observed that the weight loss at approximately 6 months post-BS was –17.9%. Observational studies have indicated that the most significant weight loss typically occurs within the first 2 years following BS [16]. In Asian populations, the average percent total weight loss after BS ranges from 20% to 25% within the first 3 years [16].
Changes in Body Weight and Other Clinical Variables after Bariatric Surgery in Korea
GLOBAL TRENDS IN BARIATRIC SURGERY
In Korea, the most common type of primary BS is SG, accounting for 75% of procedures, followed by RYGB at 12%. The International Federation for the Surgery of Obesity and Metabolic Disorders (IFSO) global registry report 2023 indicates that SG is the most frequently performed primary BS due to its effectiveness in weight loss and technical simplicity [17]. The IFSO report also notes that the majority of patients undergoing bariatric metabolic procedures are women across all reporting countries [17]. Interestingly, although women are more likely to undergo BS than men in all countries, men are disproportionately represented among those with DM undergoing these procedures. Men are more likely to report comorbidities such as DM, obstructive sleep apnea, dyslipidemia, and hypertension at the time of their bariatric procedure, whereas women are more likely to report depression [17]. The median starting BMI of participants in the registry varied from 36.1 kg/m2 in China to 47.6 kg/m2 in South Africa [17]. In our study, the mean preoperative BMI was 36.5 kg/m2, which is comparable to that in China (Table 3). In Taiwan, there has been a slight decrease in the percentage of SG procedures performed, attributed to growing concerns about the potential for postoperative de novo or worsening of preexisting gastroesophageal reflux disease (GERD), and possibly even esophageal cancer [18]. GERD affects up to 51% of patients with severe obesity seeking BS. The sleeve procedure is linked to a higher incidence of GERD (31.6% for SG vs. 10.7% for gastric bypass) and a worsening of symptoms [19,20]. It remains unclear whether undergoing a primary sleeve procedure followed by a secondary gastric bypass yields outcomes comparable to a primary gastric bypass alone, and the operative risks of any subsequent bariatric operation are significantly higher [20]. Therefore, it is important to engage in shared decision-making when selecting bariatric procedures for individual patients, such as choosing between SG and gastric bypass.
BARIATRIC SURGERY AND DIABETES MELLITUS
BS is emerging as a powerful tool for treating T2DM as well as severe obesity [11]. The choice of bariatric procedures varies depending on whether the patient has T2DM. As previously mentioned, procedures with malabsorptive components, such as RYGB and duodenal switch, are more commonly performed in patients with DM than in those without DM. The rapid improvement in hepatic insulin sensitivity shortly after surgery may result from the sudden and profound caloric restriction, while the beneficial effects on skeletal muscle insulin action appear later and are primarily driven by weight loss [21,22]. The major mechanisms through which BS exerts weight-independent effects on glucose metabolism include increased tissue-specific insulin sensitivity, enhanced beta-cell function, improved incretin responses, changes in bile acid composition, and modifications of gut microbiota [21]. Both the first phase of insulin secretion and the incretin effect, which are severely impaired in patients with T2DM, are quickly restored to near normal levels after BS, particularly following RYGB [21,23]. BS can lead to significant improvements in T2DM, although outcomes vary across different procedures and populations. In a large multicenter study involving 34 United States health systems, patients who underwent RYGB experienced greater weight loss, a 10% higher rate of T2DM remission, 25% lower rates of T2DM relapse, and better long-term glycemic control compared to those who underwent SG [24]. Besides the choice of BS procedures, other independent predictive factors also impact the likelihood of T2DM remission. These factors include preoperative insulin use, older age, higher hemoglobin A1c levels, and more complex T2DM medication regimens, all of which predispose patients to a lower probability of achieving T2DM remission [25].
CONCLUSIONS
The prevalence of class II–III obesity has significantly increased, particularly among young adults aged 20 to 39 years in Korea. Data on the effectiveness and epidemiology of BS in Korea were limited. This article reviews the trends and progress of BS in Korea from 2019 to 2022, utilizing data from the Korea NHID, a comprehensive population-based cohort database. In line with the global trend, SG was the most frequently performed bariatric procedure in Korea. The average preoperative BMI was 36.5 kg/m2, which is comparable to that of other Asian populations, and there was a weight reduction of 17.9% at approximately 6 months postoperatively. Further long-term follow-up data are required to verify the effectiveness of BS in Korea.
Supplementary Material
Supplemental Table S1.
Detailed Codes for Bariatric Surgery Procedures
Notes
CONFLICTS OF INTEREST
Mee Kyoung Kim is a deputy editor of the journal. But she was not involved in the peer reviewer selection, evaluation, or decision process of this article. No other potential conflicts of interest relevant to this article were reported.
Acknowledgements
This study was supported by a research grant (Grant No. KSSOD-2023001) from Korean Society for the Study of Obesity. The funders of the study had no role in study design, data collection, data analysis, data interpretation, or writing of the report.