What is FuelStint?
FuelStint is a fuelling analyser rather than a food diary. It takes each session from Strava and reconstructs the effort second by second, then models two things across it: how far your muscle glycogen fell, and how much you sweated out. The point is the pattern over weeks: where you keep running dry, and how much you'd need to have taken on to avoid it.
The modelling is specific enough to describe. Intensity comes from the Karvonen method using your max and resting heart rate, or from power where you have it, which is why the physiological profile step matters at signup: weight, max and resting HR, optionally body composition. Sweat loss is estimated from your weight, the intensity and the weather along the route. Runs, trail, cycling, swimming and strength all come across from Strava.
Then it turns forward. Feed the simulator a GPX of a course you're targeting and it projects glycogen and hydration over that route, which gives you a carbohydrate and fluid plan for a specific race rather than a rule of thumb. Since version 1.0 (September 2026) the simulation becomes a fuelling plan: what to eat and drink, and when, section by section. You can try the simulator without creating an account at all.
It's free, with no card, and the site switches between French and English. Version 1.0.1 is current, and the maker says some advanced features may become paid later while core access stays free.
Key Features
Second-by-second effort reconstruction
Rather than scoring a session on its averages, it rebuilds the effort across its duration and models the glycogen curve through it.
Karvonen-based intensity
Intensity is derived from heart rate against your own max and resting values, or from power for cyclists, so the same session scores differently for two riders, as it should.
Sweat and dehydration modelling
Estimates fluid loss from your weight, the intensity, and the actual weather conditions on the route, then tracks it against what you logged drinking.
GPX race simulator
Project glycogen and hydration over a target course to work out carbohydrate and fluid needs in advance. Usable without an account.
Fuelling plan
The race simulation turns into a section-by-section plan of what to eat and drink and when. You can edit each step, download the plan as a PDF with a race-day checklist, or share it as a story.
Gut tolerance training
Logging intake over time is framed as building carbohydrate tolerance deliberately, rather than just recording what you ate. You can log carbs directly or pick products from a catalogue (gels, bars, isotonic drinks), whose carb values the site calls indicative averages. Body composition is tracked over time in the Physiology tab.
It doesn't touch your Strava activities by default
The integration is read-only unless you opt in. There's an "augment my activity" toggle that adds a nutrition summary to your Strava activity description, and it's off unless you turn it on.
Who It's For
- Endurance athletes who keep blowing up late and want to know whether it was fuel, fluid or pacing
- Trail and ultra runners planning what to carry between aid stations
- Triathletes and long-course cyclists who need a fuelling plan tied to a specific course profile
- French- and English-speaking athletes
Does FuelStint sync with Strava?
Yes, through the official Strava OAuth connection. Your credentials never pass through FuelStint. It reads your activities to model glycogen and hydration, and by default writes nothing back. There's an optional "augment my activity" setting that adds a nutrition summary to the description of your Strava rides and runs, which is off unless you enable it.
Is it free?
Yes: every current feature, no subscription and no card. The site says some advanced features may become paid later and that core access will stay free.
Is it available in English?
Yes. The site has an FR | EN switch, and the public pages, the FAQ included, are in English too.
Which sports does it handle?
Cycling, running, trail, swimming and strength work, pulled from Strava. Analysis runs off power where you have it and heart rate where you don't, so cyclists with a meter get the more precise version.
Where does my data live?
In France, on OVH Cloud. Their FAQ states that tokens are encrypted and that you can revoke access at any time.
