How effective are weight-loss surgeries?
Results following surgery—including weight loss and improvements in diabetes—are influenced by several factors:
- Age
- Physical activity level
- Starting weight
- Overall health status
- Type of surgical procedure
- Adherence to postoperative dietary guidance
- Patient motivation and support from family
Weight Loss Effect
Data from Japanese patients who underwent laparoscopic sleeve gastrectomy (referenced from Seki Y, Kasama K, et al., Obes Surg 2016) show the following weight trends. The average preoperative weight was 120.4 kg, dropping to 83.4 kg one year after surgery. A slight upward trend in weight was observed starting in the third year; however, by the fifth year post-surgery, patients still maintained an average loss of approximately 30 kg.
For patients with type 2 diabetes who underwent laparoscopic sleeve bypass at our hospital (same source), blood sugar control improved significantly. The average HbA1c level—a key marker of glucose management—fell from 9.0% before surgery to 5.8% one year after the procedure. Additionally, while nearly half (48%) of patients required insulin prior to surgery, all but one were no longer using insulin one year afterward. In total, 82% of patients achieved diabetes remission, defined as maintaining an HbA1c below 6.5% without the use of diabetes medications. (referenced from Seki Y, Kasama K, et al., Obes Surg 2016)
Findings from International Studies
1) Long-Term Mortality and Survival
A Swedish study followed more than 4,000 individuals with severe obesity over 20 years, comparing those who underwent bariatric surgery with those who received nonsurgical treatment. The medically treated group showed little sustained weight loss, whereas the surgical group—regardless of procedure type—achieved long-term weight reduction. Furthermore, the surgery group had an approximately 30% lower risk of death over a 15-year period compared to the nonsurgical group.
A Canadian retrospective study found that the five-year death rate was reduced to one-ninth in the surgical group compared to those who did not have surgery. Similarly, a U.S.-based retrospective study reported that bariatric surgery was associated with a 40% reduction in overall mortality, a 60% drop in cancer-related deaths, a 56% decrease in deaths from heart disease, and a 92% reduction in diabetes-related deaths.
2) Weight Loss and Resolution of Related Conditions
An analysis involving over 20,000 patients found the following average percentages of excess weight loss by procedure:
- Roux-en-Y gastric bypass: 61.6%
- Sleeve gastrectomy: 55.4%
- Laparoscopic adjustable gastric banding: 47.5%
In terms of diabetes outcomes, remission and improvement rates were reported as:
- Roux-en-Y gastric bypass: 87.3% remission, 93.2% improvement
- Sleeve gastrectomy: 66.2% remission, 86.9% improvement
- Laparoscopic adjustable gastric banding: 47.9% remission, 80.8% improvement
Improvement rates for other obesity-related health conditions were also high, ranging from 50% to 90%.
Summary of improvement rates for obesity-related diseases after surgery (Source: CapitalSurgeons)