Is Overtraining Actually Just Undereating? Here’s The Compelling New Evidence

The term ‘Overtraining‘ is often misunderstood. You’d be forgiven for thinking that it just means training too hard, but in reality, it’s much more complicated than that.

Overtraining is a physiological state caused by an excess accumulation of physiological, psychological, emotional, environmental and chemical stress. Crucially, it’s impacted strongly by how much you eat. And while the relationship between overtraining and undereating has been explored in the past, new evidence suggests that this link is much closer than initially thought.

In November 2021, a major report into the link between overtraining and underfueling was published by an all-star cast of endurance nutritionists and exercise physiologists. The paper argued that the symptoms and measures of overtraining and undereating are 90% the same. 

Previously, overtraining has often been misunderstood and misdiagnosed, while undereating has been fairly easy to identify, given its clear connection to low carb consumption. Although it may sound obvious, simply giving yourself enough fuel greatly reduces the risk of overtraining

But why does it matter so much? Let’s look into the risks of overtraining and undereating.

Is Overtraining Actually Just Undereating Heres The Compelling New Evidence

What are the dangers of undereating and overtraining?

Overtraining isn’t just an accumulation of various stresses — the term also encompasses a ‘long-term decrement to performance capacity’ caused by this training and/or non-training related stress.

The result of this is that athletes can develop a series of maladaptations that vary depending on the individual. This basically means that instead of the body becoming better at completing particular exercises after time, it overreaches, and performance levels stagnate or decrease.

Seeing as every training session introduces stress, it’s a given that you’ll need some sort of rest and recovery afterwards. But when chronic stresses aren’t processed properly by the body, we start to see both overtraining and Relative Energy Deficiency in Sport (RED-S)

According to the authors of the study, an increased training load “tends to initially result in improvements in performance, potentially through a combination of increased training adaptations and/or initial changes in body composition outcomes”.

Essentially, this is an adaptation to training, and it’s not a bad thing in and of itself. However, what comes next can be dangerous.

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Basically, if athletes see positive results from an increased training load, they are likely to go even further, training harder still and creating a “perfect storm” for overtraining and RED-S. Pushing themselves in this way will often result in them overworking and/or injuring themselves.

This set of circumstances is often influenced by athletes suffering from Low Energy Availability (LEA). Let’s take a closer look at what exactly that means.

What is Low Energy Availability (LEA)?

In order to understand overtraining and undereating, we must understand Low Energy Availability (LEA).

Low energy availability (LEA) refers to a state in which the body doesn’t have the energy levels required to support all the physiological functions needed in order to maintain optimal health.

Basically, if your total energy intake doesn’t take into account just how much energy you’ll lose after exercise, you’re likely to experience LEA. This makes you incredibly vulnerable, even within the context of a single day of heavy training.

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For that reason, eating filling, indulgent food during post-race recovery windows is crucial when it comes to regaining strength and maintaining a healthy lifestyle.

While some sportspeople may be instructed to follow particular guidelines by doctors or nutritionists, as a general rule it’s healthy to treat yourself in this window — burgers, pizzas, burritos, whatever floats your boat!

Giving ourselves enough nutritional fuel is vital if we are to maintain the healthy functioning of the nervous, endocrine, metabolic and musculoskeletal systems (which must all be at full strength in order to encourage adaptation).

Unfortunately, many athletes find it difficult to eat well at all times. So why is this such a problem for sportspeople? 

Why do athletes often undereat?

Athletes are more likely to experience LEA than the average person, for a number of reasons. 

1. The belief that lower body weight will result in greater performance 

Reducing body weight can have a positive impact on athletic performance in areas like running velocity or jump height. Knowledge of this can lead to altered dietary habits. But it’s important to remember that so-called ‘ideal’ body shapes and sizes vary massively from sport to sport. 

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Endurance-based sports like long-distance running often require low body fat, which can cause athletes to try a variety of diets in the hope of losing weight. This can lead to greater body dissatisfaction and a higher rate of eating disorders amongst athletes. 

2. Pressure from coaches, teammates, or social media

This kind of pressure can exacerbate body dissatisfaction and dietary issues. Often, social pressures regarding body weight and physical appearance are associated mainly with women; however, male athletes are also at risk here. For that reason, it’s paramount that athletes understand the dangers of undereating/overtraining.

3. Unintentional undereating

LEA can also arise unintentionally; this is more common amongst athletes engaging in sports with high energy expenditure, like rowing or cycling. When the caloric intake and exercise intensity of these athletes don’t match up, it can lead to problems.

Chronic low caloric intake may come from something as simple as lack of knowledge about nutrition, limited time for meal prep, inadequate cooking skills, or financial reasons. It’s also worth noting that training too much can also cause you to lose your appetite, meaning you may not notice if you’re not eating enough. 

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Functional overreaching vs Non-functional overreaching

The lines between unintentional LEA and the development of eating disorders can become blurred, because over time small dietary changes can end up becoming compulsive.

According to Stellingweff’s report, short-term performance decreases from days to weeks can be split into two categories: functional overreaching (which is usually planned, designed to push an athlete beyond their limits), and non-functional overreaching (which is unplanned, and unproductive). 

We’ve now explored the relationship between food consumption and athletic performance, and explained why undereating is such an issue for athletes. But how can we actually differentiate between overtraining and undereating? 

What is the difference between overtraining and undereating?

Noting the difference between overtraining and underfueling is difficult, because virtually all the symptoms are the same. Sports Medicine‘s new study highlights how overtraining and underfueling share pathways, symptoms, and diagnostic complexities. 

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Areas that can be hit can include strength, endurance, coordination, sex hormones, and immune, metabolic and cardiovascular function, to name a few. It’s important that we recognise these connections, because they have substantial long-term health and well-being implications.

Relative Energy Deficiency in Sport (RED-S) is a consequence of LEA that has often been linked to training overload, but new findings highlight how under-fueling is just as likely to contribute to this state.

So how can athletes ensure that they aren’t impeding their performance potential by under-fueling? And how easy is it to identify performance decline?

How to explain performance decline

It can be difficult to distinguish between performance decline and the ordinary decrements or obstacles of everyday life. For example, someone who rarely exercises and eats a lot could potentially go to the doctor with a similar set of symptoms as an athlete with overtraining or RED-S.

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That being said, there are some ways that you can become a bit more certain about potential overtraining diagnoses. One two-bout exercise protocol studied by the British Journal of Sports Medicine focused on showing how performance decreases over time can help diagnose overtraining.

Reducing the intensity and volume of your workout sessions can give your body a chance to recover, and it’s important that you listen to it.

No one knows your body better than yourself, so trust your gut if you think you can identify performance decreases and signs of overtraining.

In terms of underfueling, more clarity can be provided by energy availability calculators, which can help you work out whether you’ve been taking in enough fuel and giving yourself the optimal chance of recovering. 

Scans of bone health or menstrual cycles can also help identify whether you are underfueling. Again, it can be difficult to directly link physical symptoms to underfueling, much like with overtraining, but there are things you can do to deal with both experiences.

For more on this, check out our article on how to identify and tackle signs of overtraining.

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How can athletes negate the risks of overtraining and undereating?

Some athletes or coaches may boil down their advice to one simple word — carbs! The links between eating carbohydrates and performing elite sport are well-known; we’ve all heard professional footballers complaining about early morning chicken pasta meals on matchday. 

Therefore, it may not surprise you to learn that lower carbohydrate intake has been linked to RED-S symptoms. But it’s not just this food group that’s important — giving real thought to your dietary balance is crucial when it comes to maintaining adequate energy and performance levels.

When it comes to substantial meals, think of a healthy and filling balance between protein, carbs, fruit and veg, and healthy fats.

One thing many people don’t pay enough attention to is hydration. You could be eating an enormous banquet after each intense session and giving yourself plenty of nutritional fuel, but if you’re not drinking lots of water too, full recovery will be impossible.

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So, to briefly recap, here are a few pointers to help you identify and negate the symptoms of overtraining and/or undereating:

  • Treat yourself to substantial, filling meals in recovery windows between sessions
  • Listen to your body when it feels strained
  • Do not push yourself too hard – this can cause injury, fatigue, and long-term performance decreases
  • Take rest days, and try to give yourself 48 hours between particularly intense sessions
  • Drink plenty of water at all times

Fueling the work that you do is crucial. By overtraining or underfueling, you harm your ability to recover fully, and therefore create numerous avoidable health risks.

And now that the overwhelming similarities between overtraining and underfueling are clear, it’s extra-important that runners support long-term recovery and adaptation by eating enough food, drinking enough water, and not over-exerting themselves.

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Fred is a London-based writer who works for several sport, fitness and wellness sites. He's a keen runner and amateur footballer, who also writes regularly for Jobs In Football and follows his side Norwich City home and away.

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