Drastically reducing caloric intake before competitions is a common practice among athletes, but it not only hampers their performance but can also weaken their immune systems.
Elite athletes, whether in swimming, rowing, running or cycling for events like the Olympics or Tour de France, have long focused on achieving the ‘right’ weight for optimal performance. This emphasis may be driven by a desire to appear fit or qualify for specific weight categories. There is a prevailing belief that weight loss can enhance athletic abilities.
This practice is widespread among athletes, particularly in endurance sports such as running, swimming, cycling, and rowing, leading them to reduce their food intake before competitions.
“This is especially concerning for female endurance athletes who often place a strong emphasis on weight in their sports. Consequently, they engage in short but intense periods of weight loss with the expectation of improving performance,” explains Professor Ylva Hellsten of the University of Copenhagen’s Department of Nutrition, Exercise, and Sports.
Professor Hellsten and researcher Jan Sommer Jeppesen recently conducted a study on the repercussions of low energy availability among female athletes.
“We are aware that inadequate food intake is linked to various health issues such as menstrual irregularities, compromised bone health, and metabolic changes. However, there are still aspects we need to explore. Thus, we delved deeper into some of the potential consequences,” says Jeppesen, the lead author of the study.
Decline in Performance
In their study involving twelve female triathletes with normal energy intake, the researchers observed the impact of different calorie levels on performance. During a period of reduced caloric intake, the athletes lost about 4% of their body weight, including muscle mass, leading to a decline in performance:
“A 14-day period of low food intake resulted in a 7.7% decrease in performance during a 20-minute cycle time trial, which is significant. In a more strenuous short-term test, performance dropped by up to 18%. This clearly demonstrates that such practices significantly impair athletic performance even over short durations,” explains Jan Sommer Jeppesen.
Compromised Immune System
Besides performance, the researchers also investigated the effects on athletes’ immune function:
“Insufficient energy intake led to increased systemic stress, with elevated cortisol levels, a stress hormone, and heightened stress in immune cells. This suggests a severe impact on various immune system aspects when individuals do not consume sufficient food, potentially making athletes more susceptible to illnesses,” notes Jeppesen.
The researchers aim to raise awareness about this issue through their study:
“Many coaches still push athletes to lose weight, perpetuating a longstanding practice in sports. It is essential to shine a light on this trend and question the physical and psychological effects on our athletes,” states Ylva Hellsten.
Utilizing Research Findings
Team Denmark, the Danish elite sports organization, views the research results positively.
“This study addresses a crucial issue and challenges the belief that lighter always means better. This mindset is still prevalent in many sports. I encounter numerous athletes who cut weight before competitions without understanding the consequences,” says Majke Jørgensen, a sports nutritionist and Team Denmark manager.
Jørgensen considers the results valuable in supporting their efforts:
“Elite athletes and coaches seek evidence-based critiques to address these issues. The study’s use of actual athletes as subjects strengthens the findings’ applicability to athletes and coaches supported by Team Denmark. We will integrate these results into our communication initiatives during individual sessions, workshops, and presentations,” adds Jørgensen.
Refueling Does Not Offset Effects
After a period of low energy availability, the athletes underwent a three-day “refeeding” phase, but it did not restore or enhance performance:
“Although we anticipated the three-day increased calorie intake would improve performance, no such effect was observed. Their performance remained as impaired as before the refueling phase. This indicates that the negative consequences cannot be swiftly reversed by replenishing energy stores, a tactic commonly employed by athletes,” highlights Jeppesen.
Gender Disparities in Vulnerability
Studies suggest that men are more resilient to inadequate energy intake compared to women:
“Limited research implies that men can endure reduced energy intake before experiencing negative impacts. This suggests that women, in particular, are more vulnerable in this regard,” Jeppesen notes.
The disparity is attributed to the substantial reduction in estrogen levels among women due to low energy availability. Since estrogen plays a crucial role in protecting the circulatory system, muscles, and bones, its decline significantly affects a woman’s physiology. Hellsten emphasizes that prolonged food deprivation, especially in women, can have long-lasting detrimental effects.
