Sam Runs Now: low FODMAP with a dietitian, then getting stuck in the personalisation phase

Sam, a 38-year-old learning to run, had lived for years with bouts of nausea lasting days or weeks, appetite loss, weight loss and what he calls occasional gut issues. After a doctor offered only anti-nausea tablets, he went straight to a dietitian, who suggested the low FODMAP diet as a non-invasive first step.

He kept a food diary for a month, then began elimination in late October. He describes it as very hard: a long exclusion list, no eating out, and having to restart the clock if anything slipped in. At about four weeks his symptoms stopped, and he was surprised to find his weekly headaches, much of his fatigue and his migraines had gone too. He stayed on elimination two more weeks.

Reintroduction, from November, meant testing one FODMAP group at a time in rising amounts with resets between. He found it mentally hard to make himself ill on purpose. Results: fructans were the worst, bringing headaches and nausea; lactose, mannitol and sorbitol caused milder, different gut symptoms.

Personalisation began in January but stalled. Repeated upsets while expanding his diet made him stop trying, and months on a barely widened diet left him anxious about food and, he suspects, more sensitive. He has since seen a second dietitian and is adding small amounts of diverse foods, alongside half-marathon training to rebuild appetite. He reports feeling much better overall, with occasional upsets.