Reporter says ChatGPT helped him lose 20 pounds and run faster in the Paris Marathon

The experiment

It has been reported that Bloomberg journalist Derek Wallbank used ChatGPT to build a personalized training plan as he prepared for the Paris Marathon. Can a chatbot really replace a coach? Short answer: not entirely. But Wallbank’s account suggests an AI-driven plan can nudge habits, structure workouts and keep someone accountable — enough, in his case, to change the needle.

The results and the caveats

It has been reported that the experiment ended with roughly a 20‑pound weight loss and faster race times. Allegedly, the assistant mapped out a mix of runs, recovery and nutrition tweaks that fit around his work schedule. Those are impressive numbers, sure — but they come with caveats. AI can offer structure and ideas, yet it can also miss medical risks, nuance around injury prevention, and the kind of hands‑on adjustment a human coach provides.

Why it matters

This episode is a neat, human-scale window into a broader trend: people are turning to large language models as habit engines and micro‑coaches. Wallbank’s story is as much about discipline and follow‑through as it is about code. The emotional moment? When small, consistent changes suddenly add up — and you feel it in your stride. Still, experts will warn: use AI as a tool, not a prescription. If you’re chasing PRs or carrying injuries, get a pro (or a doctor) in the loop.

Sources: bloomberg.com