Patients who lose a significant amount of weight with the use of anti-obesity medications after hip or knee replacement showed a significantly reduced risk of requiring a revision surgery compared with those whose weight remained stable, new research showed.
"These results suggest that anti-obesity medication use, with relatively safe, effective, and sustainable weight loss, may be a good strategy for improving implant survivorship among patients with obesity undergoing hip or knee replacement," wrote the authors of the research study, which was reported on February 21, 2025, in JAMA Network Open.
The results are important in light of a 2023 clinical practice guideline from the American College of Rheumatology and American Association of Hip and Knee Surgeons recommending that obesity alone should not delay joint replacement, as the procedure can represent a cost-effective and important treatment for patients with morbid obesity with severe osteoarthritic pain.
That means clinicians can likely expect to see more patients with obesity receiving joint replacement surgeries, noted first author Dongxing Xie, MD, PhD, of the Department of Orthopedics, Xiangya Hospital, Central South University, Changsha, China, and colleagues.
"With the obesity rate among patients undergoing joint replacement likely to rise further, evaluating the outcomes of post-surgery weight loss becomes imperative, as it may offer an effective means to improve implant longevity among patients with obesity undergoing joint replacement," they explained.
However, one expert cautioned that the study's lack of information about complications from anti-obesity medications and the effects of rapid weight loss after surgery need to be considered.
Hip and knee replacement surgeries are generally successful, with a revision rate of only about 1% and with a cumulative risk rate over 10 years of about 5%.
However, the risk for postoperative complications after joint replacement surgery that could possibly lead to the need for revision of surgical procedures is known to be two to three times higher among patients with obesity, the authors reported.
And those patients are very common, with obesity prevalent in as many as 50% of patients undergoing hip replacement surgery and 70% having knee replacement.
There is a lack of evidence on how weight loss after joint replacement affects that risk, with previous data indicating that fewer than 15% of patients have substantial weight loss after joint replacement.
For the study, the researchers assessed the IQVIA Medical Research Database, a large electronic health record database of general practitioner clinical systems in the United Kingdom between 2000 and 2023.
The authors identified 3691 patients (mean age, 64.7 years; 62.9% women) with obesity who underwent hip or knee replacement. Their mean body mass index (BMI) at baseline was 37.6; 63.2% of patients had hypertension, and 40.1% had diabetes. Most (74.8%) had osteoarthritis.
Using an emulated analysis with hypothetical targets, patients' weight loss was categorized as either small to moderate (2%-10%) or large (≥ 10%) after initiating anti-obesity medications within 1 year of joint replacement.
Anti-obesity medications used in the study included orlistat, sibutramine, glucagon-like peptide 1 receptor agonists (GLP-1 RA), and rimonabant.
The results showed that the 5-year risk of requiring revision was 5.6% among those with stable weight or weight gain vs 4.4% among those with small to moderate weight loss (hazard ratio [HR], 0.75 vs stable or weight gain) and 3.7% among those with large weight loss (HR, 0.57).
Stratification by the type of surgery showed that the HR for revision among those undergoing knee replacement was 0.55 in the small to moderate weight loss group and 0.49 for the large weight loss group compared with stable or weight gain.
The corresponding HRs for those undergoing hip replacement were 0.82 and 0.53.
The risks for revision over 10 years after knee or hip replacement were similar to the 5-year risks. "We observed that small to moderate and large weight loss over 1 year after initiating anti-obesity medications were associated with a 25% and 43% lower risk of 5-year revision, respectively, compared with weight gain or stable," the authors wrote.
"This suggests that weight loss after initiating anti-obesity medication improves implant survivorship for joint replacements."
They speculate that key factors of substantial weight loss that could reduce the risk for revision include a reduction of the stress placed on joint components with excess body mass, which can worsen the risk for mechanical joint failure.
Furthermore, significant weight loss could also help prevent obesity-related comorbidities such as type 2 diabetes and hypertension, which are themselves associated with an increased risk for revision.
Commenting on the study, Brett Levine, MD, chief of Joint Arthroplasty Division, MedStar Orthopaedic Institute, in the Washington, DC, region, cautioned that some key aspects of anti-obesity drugs' effects in the context of recovery from joint replacement need strong consideration.
"This is an interesting study, but there is no discussion on complications of the medications themselves," he told Medscape Medical News.
One concern, for instance, is the known rebound in weight gain if patients discontinue the anti-obesity medications. "A rebound in weight gain later is equally as concerning as the BMI at the time of the surgery," Levine noted.
Another concern is the known rapid weight loss that can occur with the newer GLP-1 RA drugs. "It is not great for people to rapidly lose weight after surgery," Levine said. "I like to see patients lose 4-5 pounds a month, maximum."
"At the end of the year, this is [about] 50-60 pounds. If the process is sustainable, then in a few years they will hit the weight they want."
In general, "controlled weight loss with a nutritionist and endocrinologist team is the better way to go," Levine added. "If these measures do not work, then maybe the medications are indicated."