A new study published in the journal Redox Biology has shown that drastically cutting calories before athletic events, which is common among elite athletes in some sports, diminishes performance and can negatively impact the immune system.
The crossover study included 12 female endurance athletes. Participants were randomized to follow either an optimized energy diet or a diet in which they only consumed about 50% of their caloric needs for two weeks while following their regular training schedule. After each period, their athletic performance was tested, and blood samples were taken. The goal of the study was to see how insufficient caloric intake affects both performance and immune system function in athletes.
The results showed that the participants lost about 4% of their body weight on average during the caloric restriction period, and about half of that was due to loss of muscle mass. Their athletic performance also worsened after the caloric restriction period, with decreases in performance ranging from about 8% to 18% depending on the task. Importantly, caloric restriction during training also led to increased stress on the immune system and increased general levels of stress hormones.
Many athletes and coaches have a “lighter is better” mentality surrounding sports and competitions, but these results suggest that weight loss before competitions may actually worsen performance and contribute to illness among athletes. One of the authors of the study stated that the impact on the immune system from caloric restriction was quite severe, and that the physical and psychological impacts of weight loss on athletes need to be reexamined. In particular, coaches and athletes should know that weight loss and caloric restriction will not improve performance for endurance athletes. This information is particularly important for female athletes, who often face increased pressure to lose weight before competitions.
Sources: Redox Biology, Science Daily