Product leader, fitness operator, and AI founder. Former Head of Product at Freeletics, now building Fuel.

Stephen is the founder of Fuel and writes most of the Fuel Journal. He builds nutrition coaching for the same audience he has shipped products to for a decade: people who take training seriously and want software that respects it.
From 2017 to 2020 he led product, design, research, content, and subscription monetization as Head of Product & Design at Freeletics, where his teams helped the digital fitness app surpass 50 million users worldwide across 100+ countries, with 70% week-one training activation. That stint — owning every surface that touches habit formation in a fitness app — is the operator lens behind every article here.
After Freeletics he grew Productboard 5x to $50M+ ARR as Senior Director of Product Management (2020–2022), reshaping the product from SMB/PLG-darling to enterprise roadmap software adopted by 6,000+ companies. Since 2022 he has been co-founder and CEO of Klu.ai, an LLM infrastructure platform used by thousands of AI teams — which is why Fuel's AI food logging and coaching feel less hand-wavy than most.
Earlier he ran global UX programs at Amazon (2016–2017) for cross-border eCommerce, led mobile investing design at Capital One (2014–2016), and spent a decade (2003–2014) running Smoov, a boutique design studio shipping work across consoles, desktop, mobile, and web. He speaks regularly at EU CPO Conference, SXSW, La Product Conf, and Product Led Alliance. Verifiable on SMW.ai, LinkedIn, and Speaker Deck.
Levothyroxine needs about 30 to 60 minutes away from breakfast and coffee and about four hours away from calcium and iron supplements. Here is how to build a morning, early-breakfast, or bedtime routine that keeps TSH stable.
How to set a daily protein target when you carry a lot of body fat and lift in a calorie deficit. Compare current weight, a realistic reference weight, and estimated fat-free mass, with worked arithmetic and the limits of the evidence.
No published study found through September 2026 validates smartwatch calorie estimates in HYROX. Plan intake from the session you expect and its place in the training week.
Current trials show no reliable performance gain from cutting gluten in athletes without celiac disease. Here is how to sort celiac disease, wheat allergy, wheat sensitivity, and exercise gut symptoms, and how to keep carbohydrate high when you do need to eat gluten-free.
In mice, fiber-starved microbes eat the gut's mucus layer. In a U.S. EHR cohort with linked dispensing data, 53.6% of adults with overweight or obesity discontinued GLP-1 treatment within a year. Ultra-processed menus added 500 calories a day. A checked roundup of the Sep 21, 2026 Huberman Lab episode.
282 articles in the Fuel Journal, newest first.
