Why Calculating the True Cost-Effectiveness of Weight Loss Drugs Is So Difficult | Research

The takeaway

Modeling cost-effectiveness of obesity drugs like semaglutide and tirzepatide faces unique challenges due to interacting uncertainties in weight regain, long-term outcomes, and duration of treatment.

Unique modeling challenge
Obesity drugs face more interacting uncertainties than typical drug evaluations due to weight regain, treatment duration questions, and large eligible populations

What the researchers found

Cost-effectiveness modeling for obesity pharmacotherapies faces unique challenges from interacting uncertainties: short trial durations, weight regain patterns, and complex relationships between weight loss and long-term cardiometabolic outcomes.

Why it matters

These modeling challenges directly affect whether insurance companies and health systems decide to cover obesity drugs — potentially determining access for millions of patients.

The numbers in context

Discusses four modeling challenges for semaglutide, tirzepatide, liraglutide, and newer agents. Considers lifetime treatment horizon and substantial eligible populations.

How the study worked

Methodological commentary analyzing challenges in health technology assessment modeling for obesity drugs, including extrapolation issues and uncertainty interactions.

Who was studied

General obese population (modeling context)

What this study cannot tell us

Commentary on methodology — does not provide new cost-effectiveness data. The challenges outlined do not have easy solutions.

How to read the evidence

Methodological commentary — provides expert analysis of modeling challenges but no new clinical or economic data.

When this study was published

Published in 2025, addressing a pressing question as multiple obesity drugs face HTA evaluation worldwide.

The bigger picture

Getting cost-effectiveness modeling right for obesity drugs is essential for health systems worldwide as they grapple with whether to cover these expensive but potentially transformative medications.

Questions still open

How should models account for weight regain when patients stop GLP-1 drugs?
Should cost-effectiveness be evaluated over a lifetime or a defined treatment period?

Common questions

Are weight loss drugs cost-effective?

The answer depends on modeling assumptions about how long patients take the drug, whether weight stays off after stopping, and how weight loss translates to long-term health improvements. This paper explains why these questions are uniquely difficult for obesity medications.

Why does cost-effectiveness matter for obesity drugs?

With over 100 million eligible patients in the US alone, even small per-patient costs add up to enormous health system expenditures. Cost-effectiveness determinations often dictate insurance coverage and patient access.

Read the original research

Challenges in Modelling the Cost Effectiveness of Pharmacotherapies for Obesity.

PharmacoEconomics, 43(10), 1171-1178

View on PubMed ↗Publisher’s paper ↗

Citation

Pennington, Becky; Cummins, Ewen; Chandler, Albany; Fotheringham, James. (2025). Challenges in Modelling the Cost Effectiveness of Pharmacotherapies for Obesity.. PharmacoEconomics, 43(10), 1171-1178. https://doi.org/10.1007/s40273-025-01520-0