A journalist recounts how he used ChatGPT to develop a fitness plan to prepare for the Paris Marathon, resulting in a 20-pound weight loss and faster race times
Six months of pain and progress, 20 pounds lost and a trial-and-error test of what AI can
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Journalist Uses ChatGPT as Marathon Coach, Drops 20 Pounds
A Bloomberg journalist turned ChatGPT into his personal fitness coach for the Paris Marathon — and it actually worked.
Bloomberg's Derek Wallbank ran an unusual experiment: he asked ChatGPT to build him a complete fitness plan for the Paris Marathon. Six months later, he was 20 pounds lighter and posting faster race times.
The project wasn't smooth sailing. Wallbank describes it as a grueling trial-and-error process, pushing through months of pain and incremental progress while figuring out where AI coaching actually helps — and where it falls short.
The results speak for themselves. The weight loss and speed improvements are real, measurable outcomes from following an LLM-generated training regimen. But the experiment also exposed clear limitations in what a chatbot can do as a fitness advisor.
It's one of the more compelling real-world stress tests of generative AI applied to personal health — no hype, just a guy, a chatbot, and 26.2 miles of pavement.