A 2025 Canadian cost model of surgery, medicines and behavioural care

Why this study matters

New weight-management medicines give people an alternative to bariatric surgery (an operation on the stomach or gut) or lifestyle programs alone. Provincial drug plans and hospitals have to decide where money goes. This model asked which options give the most health per dollar for the Canadian public payer, which in practice means provincial governments. Its conclusions differ from an earlier 2024 Canadian model, so Canadian readers may see both cited in debates about coverage.

Who was in the study

There were no real participants. The model simulated 40-year-old Canadian adults with class III obesity, meaning a body mass index (BMI) of 40 or higher, who did not have type 2 diabetes or cardiovascular disease at the start. BMI is a number that compares weight with height. The model followed this simulated group for 40 years.

What the researchers did

The researchers built a cohort-based Markov model. A Markov model divides time into cycles and moves a simulated group between health states (for example, healthy, living with diabetes, or after a heart attack) using probabilities taken from published research. The model compared six strategies: sleeve gastrectomy, Roux-en-Y gastric bypass, semaglutide 2.4 mg (Wegovy, Ozempic), tirzepatide 15 mg (Zepbound, Mounjaro), a health behaviour intervention, and no treatment. Data on treatment effects, probabilities, quality of life, and costs came from published literature. The extracted data note that the model assumed some people stopped treatment in the first year and that those who continued stayed adherent.

Effectiveness was measured in quality-adjusted life years (QALYs). One QALY is one year of life in full health. Costs were estimated from a Canadian public payer perspective. Results were expressed as incremental cost-effectiveness ratios (ICERs), the extra cost per extra QALY, judged against a willingness-to-pay threshold of CAD 50 000 per QALY.

What they found

Two strategies met the threshold. The health behaviour intervention was cost-effective compared with no treatment, at CAD 14 279 per QALY. Gastric bypass produced the highest projected QALYs (20.20) and was cost-effective compared with tirzepatide, at CAD 44 667 per QALY (R32-C135). The summary we reviewed does not report confidence intervals for these figures.

Semaglutide and sleeve gastrectomy were "strongly dominated", an economics term meaning the model projected them to cost more and produce fewer QALYs than another option. Tirzepatide was "extendedly dominated" by gastric bypass, meaning it was projected to cost more per QALY than gastric bypass. The summary states that neither medicine was cost-effective at the prices used, and that sensitivity analyses (which test what happens when assumptions change) confirmed the findings and showed that lower drug prices could improve the medicines' cost-effectiveness. The authors also noted that access to gastric bypass remains limited.

Side effects and people who stopped

The summary we reviewed does not report side effects. The model included an assumption about stopping treatment in the first year, but no rates were extracted.

What this study does not tell you

• It is a projection, not a trial. The QALY and cost figures are model outputs, not outcomes measured in real people. This is not a surgery-versus-medicine clinical comparison.
• The results depend on the assumptions and on the drug and surgery prices used. Changing prices changes the answer, as the authors themselves noted.
• The simulated population was narrow: 40-year-olds with BMI 40 or higher and no diabetes or heart disease. The model says nothing about people with lower BMI, older adults, or people with those conditions.
• The public payer perspective counts costs to government, not to people, employers, or society. A different perspective can change the result.
• A 2024 Canadian model used a different population, different comparators, and a societal perspective and reached different conclusions. The two are not directly comparable.
• Cost per QALY is not a ranking of how well treatments work for a person. Never read this model as advice about which treatment to choose.

What it means in Canada

Models like this feed into decisions by provincial drug plans and health technology agencies. They are not coverage decisions, price lists, or treatment recommendations. To learn how individual medicines are used in Canada, see semaglutide in Canada and tirzepatide in Canada. For questions about what provincial plans pay for, see public drug coverage by province.

Related reading

Other studies in this library that bear on the same question.

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