Summary: Female athletes consuming only half their caloric needs for 14 days experienced significant drops in performance and muscle mass. This low energy availability also weakened their immune systems.

The harmful effects couldnt be reversed by short-term refeeding, highlighting the risks of weight loss practices in sports. The findings emphasize the need for awareness and better support for athletes.

Key Facts:

Source: University of Copenhagen

Whether selected to swim, row or run in the Olympics, or gearing up to ride in the Tour de France, achieving the right weight has been a focal point of many elite athletes for decades. It could be to look lean and mean in a swimsuit or jersey, or to qualify for a certain weight category. But there is also a belief that losing weight enhances performance.

As such, it is a widespread phenomenon among athletesespecially inendurance sportslike running, swimming, cycling and rowingto reduce theirdietary intakein the run-up to competition.

It is particularly problematic among female endurance athletes. Many athletes focus heavily on weight in their respective sports. Consequently, they tend to go into short-term, but intense periods of weight loss with the expectation of performing better, says Professor Ylva Hellsten of the University of Copenhagens Department of Nutrition, Exercise and Sports.

She and Ph.D. student Jan Sommer Jeppesen are two of the researchers behinda new studyon the effects of low energy availability amongfemale athletes.

The paper is published in the journalRedox Biology.

We know that the phenomenon of not eating enough is associated with many things that are harmful to healthincluding missed periods, compromised bone health and changes in metabolism. But there is still plenty that we dont know. As such, we investigated some of the possible consequences more closely, says Jeppesen, who is the studys lead author.

For the study, the researchers recruited twelve female triathletes, all of whom had a normal energy intake. During one part of the trial, the athletes were given enough calories for 14 days, after which their performance was tested. The same athletes also went through a 14-day period during which they consumed only about 50% of their energy needs while sticking to their normal intensive training schedule.

During the period with insufficient calories, athletes lost an average of roughly 4% of their body weight, about half of which was muscle mass. And they experienced a loss in performance:

The fourteen days of insufficient food intake reduced their performance by 7.7% in a 20-minute time trial on a bike, which is quite significant. And during a more intense short-term test, their performance slid by as much as 18%. So there is no doubt that this practice greatly impairs ones performance as an athlete, even over shorter periods of time, says Jeppesen.

In addition to sports performance, the researchers examined the effects on athletes immune function.

Among other things, we saw that insufficient energy intake was associated with increased systemic stress. The athletes had a large increase in cortisol, a stress hormone, and a dramatically increased stress level in immune cells. This suggests that there is a quite severe impact on several aspects of the immune system if one doesnt eat enough. This may potentially contribute to athletes being more exposed to illness, says Jeppesen.

The researchers hope that the results of the study will help create more awareness of the phenomenon.

Many coaches continue to pressure athletes to lose weight. For many years, it has been a part of the culture in the sports worldand remains so. We need to shed light on the phenomenon and ask critically: What are we actually doing to our athletes both physically and psychologically? says Hellsten.

Team Denmark, the Danish elite sport organization, welcomes the new research results with open arms.

It focuses on a really important topic and challenges the attitude that lighter is always better. The theory and culture remains prevalent in many sports. I experience many athletes who trim their weight in the weeks leading up to a competition, but without understanding the consequences of doing so, says Majke Jrgensen, a sports nutritionist and manager at Team Denmark.

She sees the results as useful knowledge that can support a message that Team Denmark has been trying to promote:

My experience is that elite athletes and coaches are curious, but need research that backs up any critiques of the phenomenon. Here, the fact that thetest subjectsare actual athletes is a major strength, so that the results can be transferred to the athletes and coaches that Team Denmark supports.

We will use these results to support what we are already trying to communicate, both when we sit down with athletes one-on-one, as well as during workshops and presentations in these types of contexts, says Jrgensen.

After fourteen days of low energy availability (LEA), the athletes underwent a three-day refeeding period as part of the trial, during which they were provided plenty to eat.

We had expected that the three days of enough food would restore their performanceand maybe even improve itbut there was absolutely no effect. Their performance was just as degraded as prior to the three days. This tells us that the negative effects cannot be reversed by quickly replenishing energy stores, which is a strategy used by many athletes, says Jeppesen.

According to the research literature, men tend to be more resilient when it comes to insufficient energy intake.

Based upon the rather limited research in this area, it seems that men are able to tolerate reduced energy intake before it affects us negatively. This indicates that women in particular are a vulnerable population in this respect, says Jeppesen.

The gender difference is partly due to the fact that low energy availability can cause a womans estrogen levels to drop drastically. Since estrogen protects the circulatory system, muscles and bones, etc., estrogen loss has extensive effects on a womans physiology.

Hellsten points out that theharmful effectsof not eating enough for long periods of time, especially in women, can therefore also be lifelong.

Author: Ylva Hellsten Source: University of Copenhagen Contact: Ylva Hellsten University of Copenhagen Image: The image is credited to Neuroscience News

Original Research: Open access. Low energy availability increases immune cell formation of reactive oxygen species and impairs exercise performance in female endurance athletes by Ylva Hellsten et al. Redox Biology

Abstract

Low energy availability increases immune cell formation of reactive oxygen species and impairs exercise performance in female endurance athletes

The effects of low energy availability (LEA) on the immune system are poorly understood. This study examined the effects of 14 days of LEA on immune cell redox balance and inflammation at rest and in response to acute exercise, and exercise performance in female athletes.

Twelve female endurance athletes (age: 26.83.4yrs, maximum oxygen uptake (O2max): 55.25.1 mLmin1kg1) were included in a randomized, single-blinded crossover study. They were allocated to begin with either 14 days of optimal energy availability diet (OEA, 522kcalkg fat free mass (FFM)1day1) or LEA diet (222kcalkg FFM1day1), followed by 3 days of refueling (OEA) with maintained training volume. Peripheral blood mononuclear cells (PBMCs) were isolated, and plasma obtained at rest before and after each dietary period. The PBMCs were used for analysis of mitochondrial respiration and H2O2emission and specific proteins. Exercise performance was assessed on cycle by a 20-min time trial and time to exhaustion at an intensity corresponding to 110%O2max).

LEA was associated with a 94% (P=0.003) increase in PBMC NADPH oxidase 2 protein content, and a 22% (P=0.013) increase in systemic cortisol. LEA also caused an alteration of several inflammatory related proteins (P<0.05). Acute exercise augmented H2O2emission in PBMCs (P<0.001) following both OEA and LEA, but to a greater extent following LEA. LEA also reduced the mobilization of white blood cells with acute exercise. After LEA, performance was reduced in both exercise tests (P<0.001), and the reduced time trial performance remained after the 3 days of refueling (P<0.001).

14 days of LEA in female athletes increased cortisol levels and had a pronounced effect on the immune system, including increased capacity for ROS production, altered plasma inflammatory proteome and lowered exercise induced mobilization of leukocytes. Furthermore, LEA resulted in a sustained impairment in exercise performance.

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