Cutting Calories Won’t Bring Podium Finishes

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Attempts by endurance athletes to slash calorie intake to drop or maintain a lower body weight prior to competition can be driven by a belief that fewer pounds will enhance performance. Think about cyclists and triathletes wishing to increase their power-to-weight ratio. The thing is, cutting back on calories too drastically can hamper not benefit performance. A research team from the University of Copenhagen’s Department of Nutrition, Exercise and Sports recruited 12 female triathletes and had them undergo two rounds of performance testing. The participants ate a calorie-sufficient diet for two weeks before the first round of fitness testing, which involved a biking time trial. For the second round, athletes cut their calories by 50% for two weeks while maintaining their usual intense training schedule. The participants lost about 4% of their body weight during the calorie-cutting phase of the experiment, about half of which was muscle mass, and also performed about 8% worse on a 20-minute time trial. During a more intense short-term test, their performance slid by as much as 18%. Of concern, the athletes’ performance continued to take a hit even after a three-day recovery period where they were provided sufficient calories to meet training needs. The low energy availability led to a large increase in cortisol, a stress hormone, and a dramatically increased stress level in immune cells, suggesting that insufficient calorie intake to meet training needs can have a detrimental impact on the immune system and potentially contribute to athletes being more exposed to illness. The study authors hope these results, published in the journal Redox Biology, will increase awareness of the health and performance pitfalls of poor nutrition, both for endurance athletes and their coaches.