Austria’s Marcel Hirscher at the Pyeongchang 2018 Winter Olympic Games: what does it take to consume 8,000 calories – the equivalent of about 20 plates of lasagna – every day? Photograph: Dimitar DILKOFF/AFP/Getty

For cross-country skier Martin Moller, the biggest challenge of his sport is not the freezing cold, the hundreds of hours of training or the gruelling(...)