“We know that the phenomenon of not eating enough is associated with many things that are harmful to health – including missed periods, compromised bone health and changes in metabolism. But there is still plenty that we don’t know. As such, we investigated some of the possible consequences more closely,” said Jan Sommer Jeppesen, a lead author of a recent 2024 study from the University of Copenhagen.
Weakening of the immune system
The researchers of this study examined the effects of energy intake restriction on athletes’ immune function. They involved 12 female triathletes who went through 14 days of normal energy intake followed by 14 days of eating only 50% of their energy needs. During these periods, they stuck to their intensive training schedule and underwent testing to assess their performance and immune system. The results showed markers of weakened immunity.
“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 doesn’t eat enough. This may potentially contribute to athletes being more exposed to illness,” says Jeppesen.
Worsening bone health
This recent study builds on a lot of previous research into low energy availability (LEA) and its impact on health. Probably the most common issue caused by energy deficits in sports is poor bone health. Insufficient energy availability reduces bone formation, which increases the risk of osteoporosis in the long term and stress fractures in the short term, especially in endurance athletes engaging in high-impact sports. Bone health is discussed particularly in women’s sports under Relative Energy Deficiency in Sport (REDs). We will come back to that later in this series.
Affects mental health
Mental health is not discussed as often in relation to energy deficits but research shows that it can be a serious accompanying health problem. The International Olympic Committee says the following in their review from 2023.
“Based on currently available data, early psychological indicators associated with problematic LEA are mood changes, fatigue and psychological conflict. More severe mental health outcomes associated with REDs are reduced well-being, elevated anxiety, depressive symptoms and eating disorders.”
Disruption of almost every part of human physiology
Energy deficiency in sports is becoming an important topic. It has been shown to disrupt many different areas of human physiology such as endocrine, metabolic cardiovascular, gastrointestinal or haematological functions. And it can have a significant negative impact on growth and development, which is particularly concerning in regard to youth sports.
Thankfully, sports organisations and teams are starting to take notice. The findings of the Copenhagen study were welcomed by Team Denmark, the Danish elite sport organisation. Their sports nutritionist Majke Jørgensen said the following about it.
“It focuses on a really important topic and challenges the attitude that lighter is always better. This theory and culture remain 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.”
The consequences of energy deficits are not just about health, they could negatively impact sports performance too. We will take a closer look at that in the next article.
