The nutrition and performance science community tends to view human physiology from the perspective of evolution. When new physiological processes are understood by science, many scientists ask the question: “how was this process an evolutionary advantage?”
Evolution and natural selection allow for the most advantageous physical, mental or physiological attributes to carry through to future generations.
In many cases, we find the answer to our physical or mental ailments by going back to nature. Going back to the routines and habits of our distant ancestors allows us to reap the benefits of our hidden physiological advantages.
Some of the physiological secrets that I am referring to are:
- Cold Exposure – Exposing our bodies to cold temperatures (cryotherapy, cold baths or showers) has been argued to have been a part of our past. It wasn’t until very recently that our civilization started to use heaters or jackets to stay warm. Constantly running towards comfort tends to cause us to miss out on many physiological advantages.
- Slight stress through cold exposure causes physiological changes by activating genes associated with the conversion of white body fat to brown body fat (the metabolically active and healthy form of fat that takes up less space and keeps us warm) 
- Cold stress can also help the brain to activate the production of hormones that combat depression 
- Meditation/Breathing Exercises – Taking time out of our busy schedules to meditate for at least 10 minutes is very important. Our ancestors definitely did not sit at a desk from 9 to 5, 5 days a week. We are so preoccupied with manufactured thoughts that we tend to lose touch with our being. Even just remembering to breathe throughout the day has it’s benefits.
- Mediation has been shown to help reduce depression and improve concentration 
- Breathing exercises such as the Wim Hof (The Iceman) method have been shown to create physiological changes that defy scientific logic.  Ability to fight disease, curing depression, etc.
The methods that I have listed above are just two of thousands of possible advantages that we can gain by “looking back to nature for the answer”, as Wim Hof has said.
So when it comes to running what was our nature?
Evolution of Running
Evolutionary scientists view our ancestral roots as being rooted in hunting and gathering. Extended periods of time without food, feasting for short periods of time and running from predators.
Never have we needed to jog for hours on end. However, we have had to run for our lives for short periods of time to escape being eaten. It’s important to understand this distinction.
The Physiology of Running
Our bodies operate on three main fuel sources: glucose (carbohydrate), fatty acids and ketones.
Fatty acids are stored in our body fat and are awaiting usage in times of need. The problem is that they cannot be utilized in the brain since they cannot cross the blood brain barrier. That leaves glucose and ketones.
In the beginning of a long run, the body uses the glucose that is available from food intake or body stores (muscle storage of glucose and liver storage of glucose). After all of this glucose is utilized, the muscles can revert to using fatty acids for fuel. Unfortunately, as stated above, the brain cannot utilize fatty acids.
Marathons are very long and therefore it is very hard to maintain a consistent ingestion of carbohydrates to keep up with the immediate energy requirements.
Since carbohydrates are no longer present, the body begins to break down muscle fiber. Muscle fiber is composed of protein which can be converted into glucose through a process known as gluconeogenesis. This causes a significant decrease in muscle mass.
In the cover photo for this article, you can see two Rio Olympic gold medalists. One was a champion sprinter (Usain Bolt) and the other was a champion marathoner (Eliud Kipchoge).
The difference in muscle mass and muscle definition is very apparent. Not to mention that Eliud Kipchoge is more muscular than most marathon runners. Now, the loss of muscle mass may also be due in part to a bodily adaptation to become lighter. Lighter through a loss of body fat, loss of muscle mass and the conversion of fast twitch muscle fibers (large and used for quick movement) to slow twitch muscle fibers (small and more suitable for sustained movements). It’s as if the body sheds weight in order to move for longer amounts of time.
These types of adaptations are seen all the time. As the methods that I listed above, stresses induce positive bodily changes that allow us to thrive.
The danger arises when muscle mass is so low that other sources of muscle tissue are targeted by the body as a way to survive. These alternative sources include organs. Endurance exercise “may induce pathologic structural remodeling of the heart and large arteries.” 
How To Become Better Suited For Endurance Exercise
Going into an endurance event requiring glucose for fuel seems inefficient. It runs out quickly and can cause the breakdown of muscle tissue. Wouldn’t it be more efficient to be able mainly utilize body fat?
The amount of stored glucose in the body amounts to about 2000 calories worth of energy. The amount of stored body fat is about 30,000-100,000 calories in normal weight people. 2000 calories can be more than what is required to run an endurance event depending on the length of the event.
Wouldn’t it be nice to use all of that body fat though?
Sure the muscles could use body fat (released fatty acids), but the brain can’t since fatty acids cannot permeate the blood brain barrier. The brain uses about 25% of the human body’s total energy requirements. If the muscles go on using fatty acids while the brain still needs glucose, muscle mass is still broken down for glucose.
The answer? Ketosis
Engaging in a low carb, high fat diet can encourage your body to turn fatty acids into ketones (water soluble fat molecules) which can be used by the brain. The process of becoming ketone adapted can take anywhere from 3 days to 1 month to occur depending on genetic predispositions and dietary factors.
Going into a race ketone adapted eliminates your body’s need to break down muscle mass since it has at least 30,000 calories worth of stored fat that it can utilize. Recent research has shown the amazing benefits of being ketone adapted for endurance activities.  Muscle mass has been shown to be preserved while improving performance.
You can find more information about ketosis at the end of an article that I wrote called: The Terrifying Reality of Today’s Food Industry.
Instead of running long distances, it may be more beneficial to undergo high intensity interval training (HIIT). HIIT consists of short bursts of maximal exertion with long rest times.
This HIIT also causes activation of specific genes associated with fat loss among many other physiological changes. 
Taking a look at the cover photo should provide insight into what may be the more favorable state of existence.
 American Diabetes Association. “High Incidence of Metabolically Active Brown Adipose Tissue in Healthy Adult Humans.” [Online]. Available: http://diabetes.diabetesjournals.org/content/58/7/1526.full
 NCBI. “Adapted cold shower as a potential treatment for depression.” [Online]. Available: https://www.ncbi.nlm.nih.gov/pubmed/17993252
 Harvard Health Publications. “In the journals: Mindfulness meditation practice changes the brain.” [Online]. Available: http://www.health.harvard.edu/mind-and-mood/mindfulness-meditation-practice-changes-the-brain
 Innerfire. “Wim Hof Method Explained.” [Online]. Available: http://www.icemanwimhof.com/files/2016wimhofmethod-revealed.pdf
 NCBI. “Potential Adverse Cardiovascular Effects From Excessive Endurance Exercise.” [Online]. Available: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3538475/
 BioMed Central. “Ketogenic diets and physical performance.” [Online]. Available: https://nutritionandmetabolism.biomedcentral.com/articles/10.1186/1743-7075-1-2
 American Physiological Society. “Effect of high-intensity training on exercise-induced gene expression specific to ion homeostasis and metabolism.” [Online]. Available: http://jap.physiology.org/content/95/3/1201.full.pdf+html