In recent years, metabolic weight loss surgery has rapidly gained popularity in China, with a significant rise in surgical volume, making the choice of surgical procedure a critical consideration for surgeons. Despite being one of the most effective bariatric procedures for treating obesity and diabetes, the application of SADI-S in China remains limited. The efficacy of bariatric surgery has been extensively discussed in previous studies. In this study, weight, BMI, %EWL, and %TWL at 3 years postoperatively were significantly better in the SADI-S group compared to the SG group. A systematic review by Esparham et al. [12] reported a weighted %EWL of 83.8% and a weighted %TWL of 39.2% at 3 years postoperatively, consistent with our findings. However, other studies, such as Marincola et al. [13] reported higher %EWL and %TWL values at 2 years postoperatively compared to our results, which may be attributable to factors such as follow-up duration, preoperative BMI [14, 15], age [14, 16], and comorbidity status. Regarding SG's weight loss efficacy, Grubnik et al. [17] found in a randomized controlled trial that the %EWL at 2 and 3 years postoperatively was 78.9 ± 20.0% and 72.8 ± 22.0%, respectively, while the SM-BOSS study [18] reported %EWL values of 72.4%, 69.5%, and 61.1% at 1, 3, and 5 years, respectively. These differences may be attributed to surgical technique in addition to the factors mentioned above. Technical factors, including the type of Bougie support tube, the distance of the resection margin from the pylorus (whether or not the antrum is resected) [19, 20] during SG, and the distance between the marking point and ileum (length of the common channel) [21] during intestinal anastomosis, can influence postoperative weight loss outcomes.

The importance of waist circumference and WHtR as obesity-related indicators is increasingly recognized. This study demonstrated that the SADI-S group exhibited greater improvements in waist circumference and WHtR compared to the SG group (P < 0.05). Andersson et al. [22] noted that changes in waist circumference can be used to assess the reversal of insulin resistance. Abdominal obesity, as determined by waist circumference, is a cardiovascular disease risk marker independent of BMI [23]. WHtR reduces the influence of height on the evaluation of waist circumference and is considered an early predictor of cardiovascular disease risk, with WHtR ≥ 0.5 being associated with early health risks [24]. Pontiroli et al. [25] demonstrated that the reduction in visceral fat was greater than that of subcutaneous fat following bariatric surgery, and that improvements in metabolic abnormalities were closely related to visceral fat reduction, underscoring the importance of this evaluation index. Cui et al. [26] reached similar conclusions, particularly in the Asian population, where the mobilization of ectopic fat was more pronounced. Therefore, WHtR should be given greater consideration as an indicator when evaluating the effectiveness of bariatric surgical treatment.

The SADI-S group achieved higher remission rates across all assessed conditions, except for NAFLD, while the SG group exhibited lower remission rates, highlighting the effectiveness of the SADI-S procedure in managing obesity-related metabolic diseases. A study by Enochs et al. [5] reported similar diabetes remission rates and glycated hemoglobin levels between SADI-S and SG (SADI-S vs. SG: 4.9 ± 0.7 vs. 5.7 ± 1.8). A systematic review by Esparham et al. [12] reported remission of T2D, hypertension, and dyslipidemia in 81.3% (421/518), 62.9% (378/601), and 69.7% (248/356) of SADI-S patients, highlighting the substantial benefits of SADI-S in managing metabolic diseases. Hyperuricemia is associated with various obesity-related metabolic diseases as a risk factor [27, 28]. In this study, the SADI-S group demonstrated superior hyperuricemia remission compared to the SG group. A study by Verrastro et al. [29] on nonalcoholic fatty liver disease reported remission rates of 57% following weight loss surgery and 16% with lifestyle changes, consistent with our findings, further confirming the benefits of weight loss surgery in the remission of NAFLD. Moreover, this study found similar fatty liver remission rates between SADI-S and SG, at 74.36% and 76.32%, respectively.

In this study, all patients underwent bone densitometry and abdominal ultrasonography both preoperatively and during follow-up. Bone mineral content (T-value) of the lumbar spine and hip joints was evaluated, with abnormal bone density defined as: T-value > −1.0 SD (normal), −1.0 SD to −2.5 SD (bone loss), and < −2.5 SD (osteoporosis). The incidence of bone density abnormalities, anemia, and gallstones in the SADI-S group was 51.28% (20/39), 20.51% (8/39), and 26.47% (9/34), respectively, all higher than in the SG group, where the incidence was 28.20% (11/39), 15.38% (6/39), and 21.21% (7/33), respectively. Although no significant difference in anemia incidence was observed between the two groups, the severity of anemia was significantly higher in the SADI-S group.

No significant differences were found between the groups in blood calcium, vitamin D, or iron levels. However, the SADI-S group had lower folic acid levels and higher vitamin B12 levels, which may be attributable to differences in postoperative supplementation regimens: Lifelong supplementation with vitamins A, B12, D, and calcium is recommended for SADI-S patients, whereas SG patients typically require supplementation for only 3 to 6 months. These findings indirectly support the effectiveness of the postoperative nutritional supplementation strategy implemented in this study. Lower levels of serum ferritin, iron, and folate in the SADI-S group may help explain the increased severity of anemia in this group.

Although the SADI-S has shown significant effectiveness in improving metabolic syndrome, the management of postoperative complications is equally crucial. According to the findings of this study, it is recommended that postoperative patients undergo a long-term regimen of vitamin and mineral supplementation to reduce the risk of associated complications [30, 31].Considering the variability in patients' needs for supplements, the implementation of a personalized follow-up plan [30, 31], which includes regular blood tests and bone density assessments, can effectively prevent or mitigate complications related to metabolic surgery while also allowing for the early identification of patients' specific requirements. Furthermore, there are notable differences in the needs of patients undergoing SG compared to those undergoing SADI-S. Therefore, developing specific management plans tailored to different surgical procedures is particularly important in clinical practice. Lastly, the significance of effective communication between healthcare providers and patients should not be overlooked. Physicians should engage in comprehensive discussions with patients regarding adherence to postoperative supplementation, ensuring that patients understand the importance of these interventions. This approach not only enhances patient compliance but also contributes to a reduction in the incidence of postoperative complications, ultimately improving the quality of life for patients and ensuring the long-term success of the surgery.

Bariatric surgery is recognized as a risk factor for gallstone formation [32]. The risk of gallstones significantly increases when a patient’s %TWL exceeds 24% or when weight loss surpasses 1.5 kg per week [33]. There is ongoing debate about whether concomitant cholecystectomy (CC) should be performed. However, in patients with obesity with gallstones, weight-loss surgery combined with CC is considered safe [32, 34] and does not negatively affect metabolic disease outcomes [35]. Our center supports performing concomitant cholecystectomy during weight-loss surgery and recommends postoperative oral UDCA (250 mg three times daily) for a minimum of six months, with extended treatment based on follow-up abdominal ultrasound findings. Although UDCA can reduce the incidence of postoperative gallstones [35], more effective strategies are needed to further reduce the incidence of gallstones, which occurred in 26.47% (9/34) of the SADI-S group and 21.21% (7/33) of the SG group in this study.

This study has several limitations. As a retrospective analysis, it employed propensity score matching (PSM) to reduce selection bias; however, this approach cannot completely eliminate potential matching errors. Furthermore, the reduction in sample size after matching may compromise the statistical power of the study, thus affecting the reliability of the results. Although this research provides preliminary data on the mid-term outcomes of SADI-S and SG surgeries for obesity and metabolic syndrome in an Asian population, the small sample size limits the generalizability of the findings. Variations in the clinical characteristics of different patients may also impact the applicability of these results. To address these concerns, future studies with larger sample sizes and multi-center designs are needed. Such research will not only validate and supplement the conclusions of this study but also offer a more comprehensive assessment of the heterogeneity of surgical outcomes, providing a more robust foundation for clinical decision-making.