If you’re an active adult, chances are at some point you’ve experienced fatigue. Fatigue in healthy individuals is typically the result of overload (e.g., too much work, illness or trauma like an accident or loss of a loved one). But nowadays, experts also caution adults from too much physical exercise…saying it can overload the body’s stress response system leading to a cascade of biochemical reactions that hurt the body. They also suggest that once the body is in a diminished metabolic state, it’s harder to lose fat or worse, makes you more susceptible to illness and other disruptions. But there’s more to this story. Many functional medicine doctors and nutritionists say that each person’s stress response system is wired differently.  Once you understand what causes your stress response system to become overloaded, you can take steps to manage it while still working out hard.

First, let’s talk about the concept of metabolic reserve. According to Kris Kresser (a functional and integrative medicine practitioner), it’s the long-term capacity of cells, tissues, and organ systems to withstand repeated changes to physiological needs. He says, "think of the body as holding a charge level like a battery. If the battery charge is full, the body’s metabolic reserve is high or strong. You’re able to do a lot of work with whatever device that battery powers. But when that charge is depleted, the device stops functioning. If you have a cordless drill, for example, and the battery is run down, you can’t drill a hole because that requires more power than is available. So, when people feel drained, depressed or have no energy despite eating well and exercising, it’s an indication that his/her metabolic reserve is low."

Now, we used to think that stress was the culprit…that the burden of multiple responsibilities and the endless ‘to do’ list was elevating cortisol levels and draining our reserves. New research, however, suggests that there are two kinds of stress: hermetic and problematic stress, but it’s only problematic stress that’s an issue. Let me explain the difference. First, the body is designed to adapt to repeated changes in the environment (both positive and negative). It’s in our DNA. Some challenges are hermetic, meaning they trigger a positive adaptation. Take weightlifting, for example. When you lift, push, pull and carry a lot of really heavy things, your body interprets that as a challenge to its survival. So, when the body repairs the small tears in muscle fibers, it rebuilds them a little bit stronger so that it can meet that same challenge in the future. That’s an adaptive change that helps the body to respond to physical challenges in the environment. Hence, the stress of weightlifting is helpful.

There’s another type of challenge that’s called negative or “perceived” stress. The word perceived is important because what one person perceives as stressful, another person may not, and not all perceived stress is problematic. For example, the ‘to do’ list may include taking the dog to the vet and clothes shopping. Those things are important but not damaging to a person’s health if they don’t get done. Additionally, anything that is new...feels unpredictable or out of our control is going to feel more stressful.  These kinds of problematic events cause the brain to release hormones that tell the body to redirect its resources from energy storage, cellular repair and regeneration to energy utilization and expenditure. In prehistoric times, this is what allowed individuals to fight saber toothed tigers, for example, but the assumption is that the emergency is short term. When perceived stress persists or accumulates, however, it depletes the body’s metabolic reserve.

Doctors and exercise physiologists call the depletion of the body’s metabolic reserve many names … adrenal exhaustion, hormonal dysregulation, overtraining, to name a few. I like how Sports Nutritionist Matt Lovell and nutritionist to England’s Rugby team describes it. He says, "There have been many attempts to distinguish the causes of adrenal exhaustion and the forms of overtraining (such as with explosive versus endurance-type athletes), but the research and categorization is far from consistent." Instead, he thinks it’s more useful to think of stress-related disorders like adrenal exhaustion and overtraining as a set of interrelated pathologies. He highlights that there are literally hundreds of interactions and feedback loops that occur along the hypothalamus-pituitary-adrenal axis (HPA) or the body’s stress-response system...hence multiple points for disruption. Some people with a lot of work and family responsibilities and poor eating habits experience disruption in the form of depression and insomnia. While a fitness minded adult who practices good nutrition, proper sleep and meditates may experience a drop in libido and gain fat in his/her midsection. Everyone is wired differently and thus needs different interventions to reduce the impact of perceived stress on the body.

Interestingly, while some experts caution against too much hard exercise, Mr. Lovell has figured out how to help elite athletes who are approaching an adrenal exhaustion or overreaching state while still enabling them to play their sport. He starts with an individual history, uses lab tests to see to what degree an athlete’s stress response system has been activated and then tackles various symptoms as an integrated system. This may include 1) removing irritant foods, 2) adding supplements that support proper hypothalamus-pituitary-adrenal (HPA) axis function, neurotransmitter production and endocrine metabolism, 3) replacing any nutritional deficiencies as well as 5) making lifestyle changes to ensure an athlete is timing fueling, re-feeding and rest at optimum times.

For example, he once worked with a 21-year old rugby player who presented symptoms of fatigue – especially in the afternoon, difficulty sleeping, under-recovery following training sessions, excess body fat despite following a strict dietary regime and a number of psychological symptoms including low-grade depression. In the athlete's own words, he said he just “didn’t feel right.” After going into details about his symptoms and family history, the initial diagnosis focused on over-training combined with an inadequate intake of quality carbohydrates to allow for full muscle recovery and protein synthesis. Hence, his recommendation was for the athlete to eat more live food and protein (with a focus on stabilizing his blood sugar) along with supplementation to assist with HPA-axis support and neurotransmitter metabolism. Over time, he evolved the athlete’s protocol even more by refining the timing and quantities of his nutrition to optimize protein absorption and fatty acid metabolism. He says this was a good example of how multiple factors can create an environment that is stressful to the body. It wasn’t solely due to diet or hard exercise.

So, what are the best tips to stop the downward spiral into adrenal exhaustion or overtraining? Chris Kresser says first, pay attention to how you feel. For active, mature adults in particular, decreased performance, decreased libido and fatigue or difficulty sleeping are all signs that your stress response system has been overloaded. Second, if you’re eating a clean diet and tried taking a couple of days of rest but haven’t rebounded, there are likely other imbalances at play. That’s when lab tests that look at nutrient, hormone and neurotransmitter levels can be helpful. Cortisol levels alone can be misleading as levels fluctuate as the body deals with different physical, emotional and psychological challenges. Matt Lovell agrees and says he finds tracking the hormones cortisol, DHEA and pregnenolone together are helpful for detecting when someone is moving into a dysregulated hormone state. Here's a quick breakdown of what he watches for:

Normal
- Cortisol --> Normal
- DHEA --> Normal
- Pregnenolone --> Normal 

Resistance: Stage 1
- Cortisol --> Raised
- DHEA --> Low
- Pregnenolone --> Normal to Low

Resistance: Stage 2
- Cortisol --> Normal
- DHEA --> Very Low
- Pregnenolone --> Low

Resistance: Stage 3 or on Brink of HPA-Axis Breakdown
- Cortisol --> Low
- DHEA --> Very, Very Low (aka on fumes)
- Pregnenlone --> Low

Second, Kresser and Lovell say you need to focus on building up the metabolic reserve. In fact, that’s the most important thing you can do to improve the body’s ability to deal with problematic stress. The things Kresser and Lovell tell their clients to experiment with include: cleaning up the diet, replacing any nutrient, hormone or neurotransmitter deficiencies, increasing rest/sleep, mindful practice or meditation and making time for fun. They say the more you add those things into your lifestyle, the better your body can adapt to problematic stress.

Finally, if you’re an active adult, pay attention to exercise recovery. Exercise is not your enemy, but too much volume or too many days of maximum intensity are. It starts with symptoms of performance degradation and fatigue. That’s when a day or two of rest or scaling back training can help a person recover. The key is not to let the fatigue accumulate as it’s a tell-tale sign that the HPA-Axis or stress response system has become overloaded.

In short, keep the amount of ‘perceived’ stress low and your metabolic reserve high. It will help you deal with the unexpected events in life while allowing you to work out hard.

Hope this helps. And as always…seek strength!