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Fuelin: Rapidly Unlocking Their Next Phase of Growth

  • SERVICES

  • Technical Architecture

  • Software Development

  • UI/UX Design

  • Product Management

  • TECHNOLOGY

  • Next.js

  • React Native

Personalized nutrition for athletes

Athletes track every mile, lap, and rep- and the biometric data to go with it. Yet despite this wealth of information, even elites are often left guessing on a fundamental question: Given how I train, what should I eat, and when, in order to perform my best?


Fuelin, the brainchild of high-profile nutrition coach Scott Tindal and AI expert Jonathan Lee, answers that question. By integrating with training platforms and applying sophisticated algorithms, they help athletes fuel precisely for their training load and goals - addressing a critical performance factor that the fitness tech industry had largely overlooked. Within two years of launch, their innovative approach won them a devoted following in the triathlon community and positioned them as a rising star in the space.

The path to scale

To achieve their early success, Fuelin prioritized getting features out quickly over building a robust technical foundation. With ambitious growth plans ahead, they knew they needed to rebuild. Their tightly coupled architecture wasn’t scalable and their iOS-only codebase meant they’d have to start from scratch for Android. Importantly, their user interface also didn't match the vision they had for a premium performance product.


They wanted a partner who could both strengthen their foundation and elevate their user experience. Whitespectre offered what they were looking for: expertise in both technical architecture and user experience, a passion for the fitness space, and a track record of positioning companies to scale.

Like so many things in the software development and product world, you build a proof of concept but never get around to making sure you've built it in a scalable way, because you've suddenly got paying users and it starts growing... With you adding on code the whole time. When I came in, I said, ‘we need to build a new platform.”

Gerrit MuellerChief Growth Officer

Achieving the right technical foundation

Whitespectre partnered with Fuelin to rebuild core components of their tech stack. Our approach focused on three areas that would enable faster development, reliability, and expansion to new platforms.

  • App architecture: We migrated to React Native, creating a unified codebase that improved development efficiency and positioned Fuelin for Android expansion
  • Backend modernization: By replacing tightly coupled Firebase functions with a modern Next.js/TypeScript backend, we gave Fuelin the flexibility to scale while reducing technical debt.
  • Full-stack consistency: We implemented a T3 monorepo architecture that synchronized frontend and backend development, significantly speeding up feature development

Throughout the process, we worked closely with Fuelin to strike the right balance - avoiding too-early optimization while ensuring the system could support their ambitious growth plans and ongoing development.

We couldn’t make a mistake in rebuilding—we had to do it once, and it had to work. Whitespectre gave us the confidence that they could deliver, and they did... I saw how Whitespectre helped TechStyle build resilience and scalability at a much larger scale than Fuelin needs today. Knowing they’d done this before gave us complete confidence in their ability to handle our challenges.”

Gerrit MuellerChief Growth Officer

Elevating the athlete experience

Fuelin had always built their product with their athletes’ needs front and center. But after years of developing without a designer, both their UI and user experience had significant gaps. Working with the Fuelin team, we focused on several high-impact improvements:


  • Dynamic Home Screen & Navigation: We introduced a new home screen to serve as both command center and content hub, highlighting athletes’ next actions alongside coach insights and quick access to key views. The redesigned navigation makes navigating the app faster and more intuitive.
  • Enhanced AI Food Logging and Discoverability: We evolved Fuelin's AI-powered food logging from a traditional search UI to an engaging conversational experience, elevating its central position. We improved the visibility of powerful differentiators like sweat and carb testing, making them easier to find and use.
  • Athlete Dashboard: We created a new dashboard that gives users clear visibility into their personal stats, weight plans, training data, and nutritional recommendations, giving them a better sense of progress and personalization.
  • Intuitive Onboarding & Communication: New onboarding flows help users more easily connect their training platforms and understand key features. We improved how plan updates and algorithmic recommendations are communicated, helping athletes better understand the science behind their nutrition.
  • Premium Design System: We implemented a new visual design system that not only elevates the brand but provides a foundation for rapid feature development and consistent user experience across the platform.


These improvements preserve the heart of Fuelin's offering while making the app more accessible and engaging for both current and future athletes.

The app didn't have any UX designer involved with it before Whitespectre got involved. It was built by an engineer—and it shows. And now you can see the difference they made on UX and UI with the Whitespectre design team working on it.”

Gerrit MuellerChief Growth Officer

The results: scalable, flexible, and ready for growth

Through Whitespectre's partnership, Fuelin has transformed their platform into a robust, scalable architecture that enables rapid expansion. The modernized system improves reliability and performance while making it easier to add new features, all while preserving the sophisticated functionality their athletes depend on. The React Native migration provides a strong foundation for the Android release—already underway in-house.


Building on this technical foundation, a thoughtful redesign elevated the entire user experience to match Fuelin's brand vision. New navigation, dashboards, and guided onboarding don't just improve usability—they help athletes better understand and act on their personalized nutrition plans. Early previews at the Kona Ironman World Championships validated these improvements, with strong athlete enthusiasm for the enhanced experience.


Fuelin began as a breakthrough idea in precision nutrition. Now, they have the technical foundation to match their vision. Together, we've built a platform that can scale to serve athletes across every discipline—and we can't wait to see where they take it next.

Whitespectre is a great partner when you need someone to work with you in parallel with confidence. You can give them a product—from the idea generation phase onwards—and they’ll bring great suggestions for how to make it better from the outset. And then execute to deliver a world class product.”

Gerrit MuellerChief Growth Officer

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