Can Fit Athletes Really be Unhealthy? No Pain, No Gain

While fitness measures an individual's ability to perform a specific task, health denotes overall well-being; many athletes may be fit, but not necessarily healthy due to modern training and dietary habits.

Can Fit Athletes Really be Unhealthy? No Pain, No Gain

We often use the words “fit” and “healthy” in our everyday language to mean the same thing. If you’re fit, then surely you must be healthy. The two terms go together in commonplace language. But in actual fact, as I’ve written recently with the legendary coach and clinician Dr Phil Maffetone, the terms have entirely separate meanings. Allow me to explain.

We can define fitness as simply the ability to perform a given exercise task. For example, an elite cyclist or triathlete might possess a maximal mean cycling power output of 5.5 W/kg over 5 min, which is indicative of high VO2max power output. We can say that this athlete has incredible fitness. But that number actually doesn’t tell us much about the athlete’s health.

Health is defined distinctly as a person’s state of well-being, where physiological systems are working together in harmony to achieve a level of balance. While we typically view athletes as fit and healthy, more often than you think, they may not be.

In my past, I’ve had the privilege of working in a high-performance Olympic environment, where I was part of a team charged with helping athletes win on the world stage. Doing so involved routine case conferences with coaches focused on day-to-day problems hindering athlete preparation and performance. Reported athlete symptoms would vary, but could include anything from general persistent fatigue and muscle soreness to mental-emotional issues ranging from depression, anxiety, and lack of motivation. Often these would be associated with insomnia, and eventually reductions in performance. Fitness was typically the last to go.

The global term we place on our unhealthy athletes is that they are simply overtrained. We tend to use this expression when we can’t explain the precise problem. Essentially, however, our unhealthy athletes display nervous and hormonal systems that are battling hard against too much stress.

Stress comes in many forms, and we need a certain level of it in life to be healthy. Having no stress is equally a problem. Forms of stress include mental-emotional life stress, the stress of our physical environment (altitude, heat, pollution), and even lack of movement from sitting for prolonged periods in our offices or in automobiles commuting.

We can view the problem of the stress we experience relative to what our genetic makeup is prepared to handle. If we consider our genetic makeup to be built on a hunter-gathering background spanning ~2.4 million years, that equates to ~84,000 generations requiring large daily energy expenditures reliant on fat-burning to support the primary activities of walking, slow running, resting, and occasionally sprinting. More recently of course, there have been dramatic advances in technology through the agricultural (350 generations), industrial (7 generations), and digital (2 generations) revolutions, which today sees us living in a population adapted genetically for the stresses of life as a hunter-gatherer in the wild, but living in our high-tech, generally sedentary, overfed, and emotionally stressful twenty-first-century world.

So what we can we do about it? In our paper, we propose that two primary drivers contribute to the development of the unhealthy athlete. The first is an inappropriate volume of high-intensity training, while the second is our modern-day highly processed, highly glycemic diet. Both factors merge like a perfect storm to create a stress response that may manifest in any number of symptoms that we globally label as the overtraining syndrome.

As we go a bit deeper into the physiology of stress, we should begin by introducing our body’s central stress response system, called the hypothalamic pituitary adrenal (HPA) axis (Figure 1).

The fit but unhealthy training and eating paradigm. Photo credit: Sports Medicine Open

The HPA axis describes the complex interactions that occur among three endocrine glands: the hypothalamus (which talks to your brain and nervous system), the pituitary gland in the brain (sends regulatory hormones to other organs in the body), and the adrenal glands that sit on top of our kidneys (produce adrenalin and cortisol). Together we could call this our neuroendocrine system, and its role is to control reactions to stress, as well as the regulation of many body processes, including digestion, the immune system, mood and emotions, sexuality, energy storage and expenditure. With so many jobs involved, it doesn’t take long to realize that if the central HPA axis is out of wack, then other systems around the body also falter. A classic example that athletes may relate to is how our sex drive can be lowered under high training load conditions. In this situation, that same depressed HPA-axis turns off nearby gonad-regulating hormones and related downstream function ensues. Not tonight honey (i.e., Figure 2).

Back to the central causes of overtraining. Let’s start with training intensity. We have a sporting world currently fixated on training hard. The ‘no pain, no gain’ mantra has been around for years, but the message has become even louder through programs such as CrossFit and sport science researchers (myself included) touting the short-term benefits of high-intensity interval training. While the short-term benefits of high-intensity training are real, arising out of cellular, cardiovascular and nervous system adaptations, the sustainability of this training method without adequate recovery is unlikely. Moreover, other effects described in the figure also occur, including systemic reactive oxygen species (free radical) production, inflammation, and a metabolic substrate imbalance towards carbohydrates and away from fat oxidation.

On the other side of the equation, we have our highly processed, highly glycemic Western world diet that creates another prolonged stress (constant high glycemic load), due to our tendency to feed frequently. This often arises from a lack of satiety (feeling full) and an underlying message from nutrition authorities to feed, feed, feed. Our genetic foundation, used to fasting and fat-burning, was not equipped to handle such stress. As a result, the ensuing insulinemia is seen to advance inflammation, lower our ability to burn fat, and we observe varying symptoms of the overtraining syndrome.

The solution? While individual issues will be complex, typically solutions start with resting and recovering, and getting back to training using a lower training intensity that facilitates fat burning, along with a focus towards a whole food diet. If you’re interested in learning more, follow this link to a successful case study we published in an elite female Ironman triathlete who came back from overtraining to world-class performance using these very same techniques described.


Physical, biochemical, and mental-emotional injuries are not normal outcomes of participation in endurance sport, yet the incidence of these in our athletes is alarmingly high. Practitioners, coaches, and athletes should be aware of impending health abnormalities during training and consider periods of reduced training intensity and rest while emphasising a natural, unprocessed diet to improve health and promote fitness. For optimal performance, athletes must be both fit and healthy.

Key Points

  1. Fitness and health can be defined separately: fitness describes the ability to perform a given exercise task, and health explains a person’s state of well-being, where physiological systems work in harmony
  2. Too many athletes are fit but unhealthy
  3. Excess high training intensity or training volume and/or excess consumption of processed/refined dietary carbohydrates can contribute to reduced health in athletes and even impair performance