“Does REDs exist?” is the title of a paper we recently published (1). After many years assuming REDs was based on a solid evidence base, we started reading about the history and background behind the concept. The fact that there are far more narrative reviews than experimental studies is a bit of a RED flag (excuse the pun). The evidence was not as strong as we assumed. In this paper we raise some important questions, that are introduced below and will be explored in more detail in future blogs.
Overtraining: the REDs of the 1990s
When I went to University in the 1990s there was a lot of interest in the topic of overtraining. Everyone had an opinion about what it was, what caused it, and how it should be prevented and treated. There were lots of theories about the mechanisms and soon these theories seemed to become the explanations that were generally accepted. However, there was a problem. The actual evidence was very limited. Many studies were descriptive or anecdotal in nature. There were almost no studies that could demonstrate causal links between the suggested causes and the development of overtraining or overtraining syndrome. A wide range of symptoms were observed in athletes whose performance was not what was expected. But as mentioned above evidence was lacking, and this is not surprising because apart from the fact that it would be very unethical to study real overtraining in experimental trials, such studies would be incredible difficult to perform. This didn’t stop scientists from publishing on the topic, sharing their ideas and opinions. The number of narrative reviews was many times greater than the very small number of well controlled experimental studies. And although it is great to share theories, it becomes a problem if people start to assume that these theories are backed by a lot of evidence, and this means that the theories essentially become “facts”.
In recent years we have seen a similar scenario unfold with the topic of REDs. This area of research is characterised by a very large number of narrative reviews relative to the very limited experimental work in this area. The number of low-quality studies in this area is also alarming. Low quality, because many studies are descriptive, or have poor control and poor methods, yet often strong conclusions.
What is REDs?
We will get into this question a bit more in future blogs, but essentially REDs is a model that was developed to describe how calories (or insufficient calorie intake) causes a very wide range of symptoms. These symptoms range from disturbances in hormones and metabolism to reductions in bone mineral density, mood disturbances, fatigue and reduced performance, and even urinary incontinence. The list of symptoms is very long, keeps growing and there is considerable overlap with symptoms of the overtraining syndrome). See the infographic. These are clearly symptoms that athletes experience, and we want to make sure we can help athletes to find the causes of these symptoms.
REDs is, by definition, about calories
REDs is all about low energy availability. According to the definitions this is the only cause. But is it all about calories and energy? Can we definitively say that lack of energy causes the symptoms? Or is it carbohydrate? Or protein? Can we distinguish the effects of exercise? Exercise does more than just burn calories. It changes hormones including stress hormones? What role do other stressors play? What other explanations could there be for the symptoms? And how can we ever be certain it is "energy" if the errors in the measurements of energy intake and energy expenditure are so large?
Simplification and oversimplication
People do like simplification. x causes y. But the reality is that there may be many reasons and combinations of factors that cause symptoms. For example x, y, z in combination cause a, b, c. Oversimplification will be in the way of proper diagnosis and treatment.
Because training, stress, malnutrition, and low energy availability will all affect the central nervous system, as well as the hormonal system and these systems are likely involved in the aetiology, it is not surprising that there is so much overlap between conditions of, for example, “overtraining”, “REDs”, chronic stress or depression. Will it ever be possible to know how much of the effect is training per se, how much of it is stress? How much of it is energy? Or any other factor that can act as a stressor? This is a complex field of interrelated factors that in combination could become the cause of a range of symptoms. In the paper we identify 8 possible categories of such causes. REDs focusses on one aspect of one of these 8 categories (We have adapted the often shared figure of the REDs model to a more holistic figure that acknowledges other causes as well and does not have an energy bias.
By calling it REDs and focussing on calories (by definition) we increase the likelihood that all other factors (or causes), that are at least equally important (or sometimes more important), get less consideration.
REDs: a diagnosis of exclusion?
Sometimes it is argued that REDs is a diagnosis of exclusion. This involves a process of excluding all other factors, and if it is not one of those factors, it must be low energy availability. If this is the approach we should all agree on, why not have a method that does not have the bias for energy? A diagnosis of exclusion is also too simplistic because it assumes that symptoms are caused by a, by b or by c. It does not allow for a+b+c to cause the symptoms. An alternative approach is figuring out what the most likely causes are, using various tools that have been developed over the years.
What conclusions can be drawn about REDs?
In this paper we don't conclude REDs doesn't exist. In fact, we argue that it is impossible to conclude that REDs does or does not exist. The studies are simply not available to draw this conclusion either way. The paper just encourages people to keep an open mind, to keep challenging and keep questioning, no matter how attractive (even sexy) a theory sounds, without evidence the theory is just a theory, and a model is just a simplified version of the theory in an attempt to describe a complex phenomenon.
In the recent paper we are just asking people to be more critical and keep asking questions. Dont assume. Check and test. The purpose of this review is not to "debunk" REDs, but to challenge dogmas and encourage rigorous scientific processes. It is the duty of a scientist to do this, this is how science moves forward, so lets continue scientific discussion, lets continue to do research, in the search for better ways to help athletes.
In the next few months we will publish a number of blogs that tackle various questions that should be asked in this field. In separate blogs we will outline what is, and what isn’t known about:
LEA and performance
LEA and bone
LEA and immune function
Challenges measuring Low Energy Availability
We will also discuss:
What exactly is REDs and what is LEA?
How do you measure it and can we measure it accurately enough?
