A Series-B fitness and nutrition app — 3.4M MAU, freemium model with a $14.99/month premium tier, ~7.8% free-to-paid conversion. They were operating in a regulated space (the app makes structured nutrition recommendations, which means health-claim language is legally constrained in all three markets). Their paid acquisition through Meta and TikTok was running at $5.20 blended CPI with a D30 retention of 18%. Internal benchmark: any creator program that delivered CPI below $5.00 with comparable or better D30 retention would be considered a success. They came to us because they suspected creator-driven installs had higher intent but couldn't quantify it.
What we forecast
Forecast engine output: predicted blended CPI of $4.60 (CI: $3.90 – $5.40, 80% band). Predicted D30 retention from creator-attributed installs: 28% – 36% (vs their paid social baseline of 18%). Predicted install volume: 38,000 – 46,000 across 10 weeks.
Platform split: 45% YouTube (longer-format honest reviews, where retention math works best), 35% Instagram (Reels and Stories with swipe-up to app store), 20% TikTok (lower CPI but lower retention, used as volume layer). We deliberately under-weighted TikTok despite its CPI advantage because our model has shown for 18 months that TikTok-acquired health/fitness app installs retain 35-45% worse at D30 than YouTube-acquired installs.
Creator selection: we ranked candidates by (a) audience overlap with health-app installers (using third-party intent data we license), (b) compliance posture — creators with prior history of FDA/ASA-compliant health content, which matters more than people realize, (c) prior conversion rates on app installs (where we have data). Final roster: 14 creators across 3 markets.
We coordinated with the client's ASO team to align creator launch windows with App Store and Play Store featured-listing opportunities — creator-driven install velocity boosts store ranking, and we wanted compounding.
What we did
14 creators: 7 fitness coaches, 4 nutrition/RD creators (registered dietitians — they cleared compliance review faster and audiences trust them on regulated claims), 2 "lifestyle health" creators, 1 mental wellness creator (an experiment we'd low-confidence forecast on).
Format mix: YouTube creators produced 1 long-form review each (avg 11 min), Instagram and TikTok creators produced 2-3 short posts each. Every script went through a compliance pass — we maintain a checklist of language that triggers regulatory flags in each market. We rejected 3 initial creator drafts.
Attribution stack: deferred deep links via Branch.io, unique App Store/Play Store URLs per creator, plus self-reported attribution in the app's onboarding flow ("how did you hear about us") for triangulation.
What happened
D60 numbers: 46,100 installs at a blended CPI of $4.12 — 10.4% below our point forecast. D30 retention on creator-attributed installs: 38%, above our upper band. Free-to-paid conversion on the creator cohort: 11.2% vs the app-wide 7.8%.
By platform: YouTube CPI $5.80 but D30 retention 47%. Instagram CPI $3.90, D30 retention 34%. TikTok CPI $2.60, D30 retention 22% (within our prediction — TikTok delivers volume but the retention drag is real).
By creator type: the 4 RD creators delivered the best LTV-adjusted CPI by a wide margin — their installs converted to paid at 16%, almost double the app-wide rate. Audience trusts credentialed creators on health content in a way that doesn't apply to other categories.
ASO synergy worked. The install velocity spike from weeks 3-5 pushed the app from #38 to #11 in the Health & Fitness category on iOS US, which generated an estimated 8,400 incremental organic installs we did not attribute to creator spend. If we did, blended CPI drops to $3.48.
What we got wrong: the mental wellness creator underperformed badly — 11% of spend, 2% of installs. Audience overlap with active fitness users was lower than our model predicted. We've narrowed the audience-affinity threshold for cross-category creators.
The lesson
For health and fitness apps, retention quality from creator-acquired users is the single most important metric — CPI alone will mislead you. The compounding ASO benefit from concentrated install velocity is also real and consistently under-modeled in agency reporting. If you're not measuring incremental organic lift from creator campaigns, you're undervaluing the channel by 15-25%.
What it means for your campaign
If you operate a freemium app in a category where audience trust matters (health, finance, education, parenting), creator-led acquisition will outperform paid social on LTV almost every time — but only if you align with ASO windows and only if your compliance process can move at creator speed. Do not run this playbook if your free-to-paid funnel converts below 4% at baseline; the upstream economics won't carry it.