Observational study finds bariatric surgery patients lose significantly more weight than GLP-1 medications — Evidence Review

People with obesity who undergo bariatric surgery lose about five times more weight over two years than those using GLP-1 medications like semaglutide or tirzepatide, according to a large real-world study by NYU Langone Health. These results align with prior research showing surgery produces greater and more durable weight loss than non-surgical interventions.

• Multiple systematic reviews and long-term observational studies consistently find bariatric surgery leads to significantly higher weight loss than non-surgical treatments, including medications, over both short and extended durations, with typical total weight loss ranging from 20% to 30% or more at 1–5 years and sustained benefits for many patients 1 2 3 4 5 11 12.
• Real-world data indicate that average weight loss with GLP-1 medications outside of clinical trials is lower than trial results, with high discontinuation rates and less dramatic outcomes than initially reported 9.
• While GLP-1 agonists have generated considerable public interest and are effective for some patients, studies show bariatric surgery remains the most effective and durable option for significant weight loss, especially in those with higher BMI or those who do not achieve sufficient results with medications 1 2 3 4 5.

Study Overview and Key Findings

The rapid adoption of GLP-1 medications for weight loss has sparked debate about their effectiveness compared to established surgical treatments. Despite the popularity of drugs like semaglutide (Ozempic) and tirzepatide, real-world outcomes may differ from clinical trials due to factors like adherence and discontinuation. This study, presented at the 2025 American Society for Metabolic and Bariatric Surgery (ASMBS) Annual Meeting, provides one of the largest comparative effectiveness analyses, leveraging electronic medical records to compare weight loss outcomes for over 51,000 patients treated with either metabolic/bariatric surgery or GLP-1 medications across two major health systems.

Property	Value
Organization	NYU Langone Health, NYC Health + Hospitals
Authors	Avery Brown, Karan R. Chhabra
Population	Patients with BMI at least 35
Sample Size	n=51,085
Methods	Observational Study
Outcome	Weight loss after bariatric surgery vs. GLP-1 medications
Results	Bariatric surgery patients lost an average of 58 pounds.

Literature Review: Related Studies

To contextualize these findings, we searched the Consensus research database, which indexes over 200 million scientific papers. The following search queries were used to identify relevant literature:

1. bariatric surgery weight loss effectiveness
2. Ozempic weight loss comparison studies
3. average weight loss bariatric patients

Below, we summarize key themes from the literature and their main findings:

Topic	Key Findings
What is the comparative effectiveness of bariatric surgery versus non-surgical interventions (including GLP-1 medications)?	• Bariatric surgery consistently leads to greater weight loss and comorbidity improvement than non-surgical interventions, including medications, in both short- and long-term studies 1 2 3 4 5 11 12. • Real-world studies show GLP-1 medications result in modest weight loss (~4–7% at 6–12 months), often less than in clinical trials 9.
How durable and long-lasting is weight loss after bariatric surgery?	• Most patients maintain significant weight loss (20–30% of baseline weight) over 5–10 years after bariatric surgery, with some regaining weight but the majority experiencing sustained benefits 3 4 5 13. • Long-term follow-up indicates that Roux-en-Y gastric bypass and sleeve gastrectomy are both effective, though reoperations are not uncommon 3 5 13.
What are the real-world trends and outcomes of GLP-1 medication use for weight loss?	• Public interest and off-label use of GLP-1 agonists (e.g., Ozempic, Wegovy, Mounjaro) for weight loss has surged, but adherence is low, and discontinuation rates are high (up to 70% at one year) 6 7 10. • Observational studies suggest real-world weight loss with semaglutide is lower than in clinical trials, with average loss of 4–7% 9.
What are the risks, adverse events, and rates of discontinuation for surgical and pharmacologic treatments?	• Bariatric surgery carries a risk of major adverse events (2–5% within 30 days, depending on procedure) and a notable reoperation rate, but overall mortality is low and long-term health benefits are substantial 1 2 3 5. • GLP-1 medications are associated with gastrointestinal side effects and high rates of discontinuation due to cost or tolerability 9 7.

What is the comparative effectiveness of bariatric surgery versus non-surgical interventions (including GLP-1 medications)?

The new study's finding that bariatric surgery results in approximately five times greater weight loss than GLP-1 medications at two years is strongly supported by multiple systematic reviews and large observational studies. These prior works consistently show surgery leads to much higher and more durable weight loss than medications or lifestyle interventions, including in populations with high BMI.

• Systematic reviews and meta-analyses indicate that surgical patients lose 20–30% or more of their baseline weight at 1–5 years, compared to 4–7% with non-surgical interventions 1 2 5.
• The magnitude of benefit persists across different types of bariatric procedures, with both sleeve gastrectomy and gastric bypass outperforming medications 1 2 5.
• GLP-1 medications are effective for some, but real-world outcomes are lower than in trials, with many patients discontinuing treatment within a year 9.
• The comparative advantage of surgery is maintained across diverse populations and settings 3 4 12.

How durable and long-lasting is weight loss after bariatric surgery?

Relevant studies demonstrate that bariatric surgery not only produces greater weight loss initially, but that these results are generally durable over periods of 5–10 years or more. Although some patients experience weight regain, the majority sustain significant reductions in body weight and improvements in comorbidities.

• Ten-year follow-up studies show most patients maintain more than 20% weight loss after Roux-en-Y gastric bypass, with about 30% achieving over 30% loss 3 4.
• Sleeve gastrectomy and gastric bypass show similar long-term effectiveness, though reoperations are not rare 3 5 13.
• A standardized definition of ≥20% total weight loss is proposed as a marker of good response following bariatric surgery 13.
• Remission of diabetes and other comorbidities commonly occurs post-surgery and is closely tied to the degree of weight loss 11 12.

What are the real-world trends and outcomes of GLP-1 medication use for weight loss?

There has been explosive growth in the use and public interest of GLP-1 receptor agonists, but real-world effectiveness is limited by adherence and discontinuation. Weight loss outcomes in routine care are typically lower than those seen in clinical trials.

• Google Trends and epidemiological studies show a dramatic increase in searches and prescriptions for GLP-1 medications, especially Ozempic and Mounjaro 6 7 10.
• In real-world cohorts, average weight loss with semaglutide is 4–7% at 6–12 months, and discontinuation rates exceed 50–70% at one to two years 9.
• Off-label use for cosmetic weight loss is rising, contributing to supply shortages and raising new clinical considerations 6 7.
• The discrepancy between clinical trial efficacy (up to 15–21% weight loss) and real-world effectiveness underscores the importance of considering adherence, cost, and tolerability 9.

What are the risks, adverse events, and rates of discontinuation for surgical and pharmacologic treatments?

Both bariatric surgery and GLP-1 medications carry risks and challenges. While surgery is more invasive, it is also associated with greater long-term weight loss and health benefits for eligible patients.

• Short-term adverse event rates for surgery range from 2% to 5%, and reoperation rates vary by procedure, but mortality is low and long-term outcomes are favorable 1 2 3 5.
• GLP-1 agonists are generally well-tolerated but frequently cause gastrointestinal symptoms, and adherence is limited by cost and side effects, leading to high dropout rates 9 7.
• Most surgical patients experience improvement or remission of obesity-related comorbidities, while medication outcomes are more variable and often depend on continued use 2 11 12.
• The choice between surgery and medication should be individualized, balancing efficacy, risk tolerance, and patient preference 1 2 5 9.

Future Research Questions

Despite robust evidence favoring bariatric surgery for substantial and durable weight loss, important questions remain about optimizing treatments, long-term comparative effectiveness, and patient selection. Further studies are needed to clarify which patients benefit most from each approach and how best to integrate emerging pharmacological options.

Research Question	Relevance
What are the long-term (5-10 year) comparative outcomes of bariatric surgery vs GLP-1 medications for weight loss?	Long-term real-world data for GLP-1 medications are limited, and it's unclear how sustained their effects are compared to surgery, which has well-documented durability 3 4 5.
Which patient characteristics predict better response to GLP-1 medications vs bariatric surgery?	Identifying predictors of treatment response could help tailor interventions and improve outcomes, as not all patients respond equally to either approach 2 5 9.
How can adherence and durability of GLP-1 medication use be improved in real-world settings?	High discontinuation rates limit the effectiveness of GLP-1 medications outside of trials; understanding barriers to adherence is essential for maximizing their benefit 9 7.
What are the cost-effectiveness and health economic impacts of surgery vs GLP-1 medications for obesity?	Cost is a significant barrier to both treatments, and robust economic analyses are needed to guide policy and access decisions, especially as new medications are introduced 2.
Can combination strategies (surgery plus GLP-1 medications) enhance weight loss and maintenance compared to either approach alone?	Combining modalities may offer synergistic benefits for certain patients, but this approach has not been rigorously studied and warrants further investigation 1 5 9.