Persistence, not weight loss, is the metric that decides your ROI
Every vendor leads with average weight reduction. The number that actually determines whether your spend produced anything is how many members are still on therapy at month twelve.
Why weight loss is the wrong headline
Average weight reduction among active members is the most reported and least decision-relevant number in this category. It describes people who are still in the program. It says nothing about the members who generated cost and left.
Consider two vendors reporting identical average weight loss. One retains most members at twelve months; the other retains a fraction. Their reported outcomes look the same. Their cost per durable outcome differs by multiples.
Where members actually drop off
Discontinuation concentrates in two places. The first is early titration, driven mostly by gastrointestinal side effects and insufficient clinical contact during dose escalation. The second is the transition to maintenance, where the visible progress that motivated the member slows and the support model often thins out at exactly the wrong moment.
Both failure points are addressable by program design, which is precisely why persistence is the fairest basis on which to hold a vendor accountable. It is substantially within their control.
How to hold vendors to it
Require intent-to-treat persistence at 6, 12, and 24 months, reported on a claims-compatible key so you can verify it independently.
Tie a meaningful share of any performance guarantee to persistence rather than weight loss. Vendors that resist this are usually telling you where their weakness is.
Track cost per member who reached and maintained a clinically meaningful response, not cost per enrolled member. It is the only figure that describes what you actually bought.
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