How Healf used incrementality to defy ad platform narratives and rebalance a 90% Google budget
As the second-fastest growing company in the United Kingdom, Healf faced a familiar challenge: Could the same marketing mix that delivered rapid early growth continue to scale efficiently? Was their 90% Google ad spend really driving sales and new customers — or was it demand that would convert anyway? Conflicting signals from attribution tools only added to the uncertainty.
To move forward with confidence, Healf partnered with Paramark to make incrementality their source of truth, replacing ad platforms’ reporting narratives with causal evidence and using experimentation to guide how they allocate spend.
Because the U.K. market has unique characteristics that sets it apart from the U.S. and other countries, Healf turned to Paramark for a custom approach. Together, we optimized their channel mix and implemented incrementality as their “gold standard” for scalable growth.
Who is Healf?
Healf is a high-scale, United Kingdom-based online retailer focused on health and wellness products, primarily supplements, vitamins and functional health goods. They were named the U.K.
Founded in 2020, the company operates a curated marketplace model: rather than selling a wide range of brands, Healf selects products based on ingredient standards, formulation quality and regulatory compliance, similar to Thrive Market or Whole Foods in the United States.
On their web marketplace, they offer more than 5,000 products. The company reached £40 million in annual sales in 2025, growing more than 400% in a three-year period.
The problem: Conflicting platforms, no single source of truth
In late 2024, Health had no single source of truth about their spend. They were allocating 90% of their performance marketing budget on paid Google search. But different ad platforms and attribution tools told them conflicting information about whether Google was truly driving new customers and sales, or whether they should invest that spend elsewhere.
Their multi-touch attribution tool, for example, was pushing them to spend more on Meta, while a different last-touch model favored Google.
Healf’s team keenly recognized the pitfalls of click-based attribution. Still, they wondered whether they were ready for Marketing Mix Modeling (MMM) and incrementality. Ultimately, after speaking with Paramark, they determined there was no other method that would reveal the true story about their optimal ad spend and give them direction about where to invest next.
“The existing attribution models don’t capture the uniqueness of our customer journey.”
– Leo Laurence, Performance Marketing Lead, Healf
Why Healf determined Paramark was the ‘natural’ next step
Because the team only looked at only touches and clicks, they lacked a real cause-and-effect reasoning behind which platforms were driving ROAS. Healf’s attribution stack could not capture their customers’ cross-channel and cross-device activity, plus their data was incomplete due to online privacy restrictions.
“The existing attribution models don’t capture the uniqueness of our customer journey,” Laurence said.
They wanted to make smarter budget decisions to scale their marketing spend while maintaining a positive relationship to ROAS new customer acquisitions.
Healf had never done incrementality testing, and they sought out Paramark’s test design expertise across a diverse portfolio, including other global direct-to-consumer brands.
“We knew that all big e-commerce businesses are doing [incrementality testing],” Laurence said. “It was a natural transition.”
“[Paramark] gave us the confidence we needed,” he added.
While the Healf team briefly explored an e-commerce MMM tool, their early results weren’t trustworthy. They saw that Paramark’s method was based on multiple industry models, offering a customized, battle-tested approach.
Importantly, Paramark also understood the distinctive features of the U.K. ecosystem that differentiate it from the U.S. While other measurement tools take a cookie cutter approach to all geographies, we designed our model and testing plan especially for Healf’s operating context.
The unlock: How Healf proved Google drives growth — but not in the way they expected
The first test we ran was a geographical holdout test to determine whether Google Ads were driving net-new revenue and to quantify how incremental that impact was.
“The test was enlightening,” Laurence said, and it set the bar for future testing and Google spend.
Using a holdout strategy — reducing spend in some regions and maintaining consistency in others — we unlocked three key findings:
Google spend is incremental. Reducing spend led to a measurable decline in sales.
We set a clear incrementality benchmark. We translated platform ROAS into true business impact.
New customer spend was ~3× more incremental than existing customer spend. This was an interesting finding for a retailer competing with other retailers for customers that are already loyal to a brand, but not necessarily loyal to where they buy. It showed more customer stickiness to the retailer, Healf, than initially expected.
“Existing customers often search for one of the brands that we stock rather than Healf ourselves. There is always an element of competition,” Laurence said. “The test validated the fact that new customer spend is a lot more incremental.”
The test validated that Google was driving growth for Healf, not just capturing existing demand. Plus, it challenged the team’s assumptions about how existing customers search for and buy health products in a multi-brand retail environment.
Another test revealed that Google Search was more incremental for the brand than Google PMax, inspiring the team to shift more of their Google budget toward search, instead.
“The first test was enlightening. It's given us a deeper understanding of our existing channels and it's actually encouraged us to change our existing channel mix.”
– Leo Laurence, Performance Marketing Lead, Healf
How incrementality optimized Healf’s high-scale spend by revealing business impact, not just clicks
Paramark helped unlock a sense of confidence among Healf’s team about how they optimize their digital-first spend.
“It's given us a deeper understanding of our existing channels and it's actually encouraged us to change our existing channel mix,” Laurence said.
After the initial Google test, the Healf team calibrated their day-to-day performance metrics against the incrementality test’s benchmark of success. They also prioritized their new customer acquisition budgets.
To this day, the team refers back to the initial holdout test as an anchor for their spend allocation.
And while the team was initially skeptical about pulsing down Google spend during a high-growth phase, the takeaway was ultimately far more valuable, Laurence said.
“It’s changed how we approach measurement,” he explained. “We now have a more granular view, based on our incrementality testing, of how we should be optimizing different [spend].”
As Healf scales beyond £40M, what’s next?
Healf’s foray into incrementality became a critical lens for “all areas of the business,” Laurence said.
“People have become more fluent in the concept, and it’s a key part of decision-making.”
In 2026, the brand started to experiment with an internal multi-touch-attribution tool. One key source of truth to calibrate the new tool is their incrementality readout from Paramark.
Any high-scale marketing team should adopt incrementality as the “gold standard” for proving their concrete impact, Laurence said.
“The assumption is that by spending money you're going to see returns — the definition of incrementality.”
