August 2026 · seven days
Seven days. One app. Not a line of Swift to my name.
I gave myself a week to build an iPhone app, having never built one. Not to become a developer — to stop being the person in the room who couldn't tell whether a build estimate was honest.
Why a calorie tracker, of all things.
I'm a partner and investor in the 8 Week Transformation Challenge, and product decisions there kept arriving on my desk. I could describe what I wanted clearly enough. What I couldn't do was tell you whether the answer that came back — three weeks, say — meant three weeks of real work or three days and a comfortable margin.
That gap had bothered me for years. So I picked a Monday and gave myself until the next one.
A calorie tracker because I'd open it every day. Build something you don't use and you'll ship something nobody wants.
What actually exists at the end of it.
Fuel8. A calorie and macro tracker with 13,521 foods bundled inside it, so it works in aeroplane mode. No account, no password, no server holding your food diary — everything sits in an encrypted store on the phone itself. You log a meal by typing it, scanning the packet, tapping a saved plate, or just saying it out loud.
It is not on the App Store. It runs on my phone, it is version 1.0 build 24, and submitting it is the next thing I don't know how to do. There's no export feature either. I'd rather say that than pretend the week ended tidier than it did.
The AI wrote almost all of the code. It made almost none of the decisions.
This is the part worth copying, and it's the opposite of how it gets sold. The scarce thing was never the typing. Every choice below is a product decision, not a technical one — and every one of them is why the app is worth using rather than just worth demoing.
- The food database ships inside the app, so it works with no signal
- No accounts, no passwords, no server holding anyone's food diary
- Food on a future day is a plan until you confirm you ate it
- No streaks, no red failure states, no scores, no goal dates
- Exercise never adds calories back
- Everything free that the big trackers charge for
- Swift I have never written and still couldn't write unaided
- The data layer, the encrypted local store, the barcode pipeline
- On-device speech recognition wired into the logging flow
- The test suite that enforces the rules above on every build
- Hundreds of small fixes I described in English, not in code
Fifteen years of building companies taught me which of those decisions matter. The AI closed the distance between knowing that and having it running on a phone.
What changed on the other side of it.
I can brief properly now
I can sit with the developer on the Challenge and describe what I want in terms that survive contact with the actual work — because I've now done a small version of that work myself.
I know what's cheap and what isn't
Some things I assumed were hard took an afternoon. Some things I assumed were trivial were the reason a whole day disappeared. You cannot buy that intuition from a consultant.
The estimate conversation is different
Not adversarial — better. I ask sharper questions, I get straighter answers, and nobody has to pad a number to protect themselves from a client who doesn't understand it.
This is the whole argument behind what I do for other businesses. I don't hand over a strategy deck about AI. I use it in my own companies first, then install what actually worked.
The 8 Week Transformation Challenge.
The business this was all in service of. Eight weeks of coached training and nutrition built around you, a private community of thousands doing the same weeks, and a cash recognition for the best transformations. Challenge 31 puts £50,000 behind them.
20,000
Transformations completed
£310K
Paid out to members so far
£50,000
For the best transformations · Challenge 31
£1M
The number we're working towards
I'm a partner in the Challenge and an investor in the business, and I earn a commission on sign-ups through these links. Fuel8 is free because of it.
Want AI doing this inside your business?
I learned it on my own P&L, not on your budget. Fee, equity or hybrid.