What happens if you eat too little over a long period of time?

Joëlle Flück 23. March 2021

Too low energy availability can have a negative impact on various bodily functions and affect both women and men.

This article is presented by the Swiss Sports Nutrition Society

The health of athletes should be the top priority. From a nutritional perspective, this involves consuming the right nutrients according to the training and energy requirement. However, it is often the case that athletes don’t consume enough energy or use more energy than they consume. This can happen for various reasons, such as the availability of food, a loss of appetite or at most, a reduced intake due to intentional weight loss. Eating disorders can also be a cause and are common in sports, especially in weight-related (e.g., judo, rowing) and aesthetic sports (e.g., ice-skating, rhythmic sports gymnastics) as well as in endurance sports or female athletes. The reasons for developing eating disorders are complex and multifactorial and are not discussed further in this article due to space. This is more about describing the health effects of too low energy availability.

What is too low energy availability?

As already mentioned, energy availability is calculated by taking the energy consumed during training away from the energy supplied over the entire day and dividing it by the fat-free mass. This gives a rough indication of how much energy the body has at its disposal to maintain its physiological bodily functions (e.g., hormone production, bone density, cardiovascular system, etc.). If this is extremely low in relation to the fat-free mass, then it is referred to as too low energy availability or in technical jargon, RED-S («Relative Energy Deficiency in Sport»). Thus, if energy availability in the body is too low for a long period of time (several weeks, for example), the body has too little energy available to keep the body and its functions «healthy». Bone density can deteriorate and, in the worst case, lead to a fatigue fracture. Hormonal disorders can also occur and, last but not least, women can often have irregular menstrual periods. Gastrointestinal tract disorders, depression or diseases of the cardiovascular system can also occur. For athletes, this means an increase in the risk of injury and infection, a reduction in performance capability and muscle strength, and a decrease in recovery capability. This ultimately leads to reduced training performance and impaired performance development.

In order to protect athletes and their health, it is important to impede these long-term consequences of too low energy availability, i.e., to combat the emergence of the problem through prevention. The health of athletes can be promoted on a sustained basis by undergoing regular sports medical examinations by an interdisciplinary network of experts such as sports physiotherapists, sports psychologists, and sports nutrition consultants. Applying sports nutrition principles can also ensure an optimal energy supply before, during and after training units. If there is still a relative energy deficit, this interdisciplinary network can work together with the athlete to support the therapy.

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