Early this year, weight care company Found Health reached out to Emily Sundberg, the author of business newsletter Feed Me, inquire about sponsoring one of her daily sends on Substack. She and the Austin, Texas-based company then worked together over several months to survey her readers on how they use—and feel about—weight loss medications.
In July, Sundberg published a newsletter headlined “1 in 3 Feed Me readers surveyed use a GLP-1.” Despite being sponsored by a company that sells weight-loss medication, the post doesn’t shy away sharing its negative perceptions. In one anonymous quote submission, a reader said, “It’s kind of cheating, shouldn’t we all work to get healthy, not thin?” Another said: “I am still embarrassed for other people if they get on them.”
According to Cassi Gritzmacher, head of brand marketing and communications at Found, that’s exactly why the company inked a partnership with Sundberg. “We have to figure out how to reduce the stigma” that surrounds GLP-1s, she says. “And I think part of the key to that is surfacing these insights and sparking the conversation.”
Found’s main goal in sponsoring a Feed Me post was to build brand affinity, per Gritzmacher. Because of this, the company measured its success through engagement metrics like open rate, read time, comments, and shares, rather than last-click sales. “We’re thinking about it in a more non-traditional way that might drive your CFO nuts,” Gritzmacher says.
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She says that more than 1,000 readers took Sundberg’s survey and the resulting post “far exceeded” common open-rate benchmarks. Gritzmacher declined to share how much her company paid Sundberg, whose newsletter had about 60,000 readers as of February, according to the New York Times.
Found is far from the first brand to collaborate with a writer on Substack. With 50 million-plus active subscriptions, 5 million of which are paid, the platform has become an attractive influencer marketing channel for businesses who want to reach engaged, niche audiences.
Newsletters can lend legitimacy to small businesses
Hasnain Baxamoosa, the founder of job application tracking tool provider GigHQ, says he decided to partner with Melanie Ehrenkranz, author of the newsletter Laid Off, which publishes on Substack, after discovering her through LinkedIn. GigHQ typically advertises through Google, Meta, and Reddit, but those platforms can’t guarantee that its ads will reach unemployed people. Baxamoosa figures that the audience of Laid Off, on the other hand, is much more likely to be on the job hunt.
Ehrenkranz, whose newsletter has more than 11,000 subscribers according to its Substack page, presents a unique partnership model to brands. For just $500, they can sponsor a Laid Off post and also offer 10 readers the chance to receive a $10 gift card to a coffee shop through an automatic raffle.
By sponsoring the newsletter through this model, Baxamoosa reports that GigHQ’s website gained “just shy of 100 visits” and 25 to 30 signups. That was less than the company’s target, but still, Baxamoosa founded GigHQ just 11 months ago. As such a newly minted business, he says, building an association with a trustworthy, authentic brand like Ehrenkranz’s was worth the investment.
GigHQ will likely experiment with one or two more Substack partnerships this year, according to Baxamoosa. He hopes that directing readers to a personalized landing page will help the Austin, Texas-based company attract more customers. “There’s no magic silver bullet, there’s no easy answer,” he says. “You just gotta try some things and see what happens.”
If you offer more value, you’ll get more attention
Wealth tracking platform TenYour has also advertised on Laid Off, though founder and CEO Joah Spearman says he did things a little differently. When Spearman launched his Sacramento, California-based company in 2023, he asked his more than 140,000 LinkedIn followers to fill out a survey that’d give TenYour insights into how people make financial decisions amidst layoffs and who might benefit from its saving plan products in exchange for $50.
Once the company raised capital last year, investors asked Spearman for proof that he could expand beyond his sizable LinkedIn following—so he turned to Substack. TenYour has so far partnered with three newsletters: Laid Off, the D.C. events-focused High Vibe by Onose, which has more than 5,000 subscribers, and the R&B music-focused Yams Magazine, which has more than 1,000.
Spearman asks each publication to share his survey with its readers, offering to pay each person who fills it out $25 and to pay the writer $25 per referral. “If 10 people take the survey,” he says, “that’s $250 to people who took the survey, $250 to the creator.”
These partnerships have helped TenYour gain plenty of survey responses, but they acquire fewer customers than Spearman’s LinkedIn posts. The company typically captures one in six survey respondents as customers via LinkedIn, compared to one in nine via Substack. Still, Spearman says TenYour has grown its “email subscriber base 400 percent so far in 2025—and that is largely on the strength of these Substack partnerships.”
Spearman prefers Substack partnerships over Instagram partnerships, which he has tried in the past, because their footprint “is longer lasting.” Another plus, he says, is that when you reach out to a Substack writer, you often get to speak with them directly—rather than with a manager—because they’re still early in their monetization journey.
Substack is “first and foremost about storytelling,” Found’s Gritzmacher says. “So it works best for brands that have a slightly more complex or maybe misunderstood topic that they want to dive into, where that trust and credibility really matter, and throwing up a quick ad isn’t going to necessarily break through the noise.”
“It’s also a great way to reach people who actually care without dropping millions on a Super Bowl commercial or a celebrity endorsement,” she adds.