Can Running from a Tiger Make You Fat?

Which is Harder? Fleeing From a Tiger or PR’ing Fran?

P.S. on a hormonal level, your body doesn’t know the difference.

Most of us have heard the term “fight or flight response”, which refers to our body’s automatic ability to prime itself for action in situations that it deems life threatening. The fight or flight response is ruled by our sympathetic nervous system.


Obviously if we find ourselves stranded in a tropical mangrove swamp with a ferocious tiger hot on our heels, we would expect our body to do it’s thing to get us the Hell out of danger. Our pupils would dilate, our heart rate would increase as would the force of our heart's contraction. The bronchioles (the passageways through which air passes to the air sacs of the lungs) would dilate to allow us the most oxygen possible. Sweat secretion would be activated to keep our body temperature down. A number of blood vessels would be constricted including many of those in the skin, digestive tract and kidneys in order to shunt blood away from those organs not necessary to immediate survival. Blood flow would then be prioritized to the organs directly involved in the physical activities required for escape. These actions are 100% automatic and are the result of the secretion of a cascade of hormones including epinephrine, norepinephrine and cortisol.

Now think back to the last time you did “Fran”. How many of those “Tiger Fleeing” stress responses were present? Most likely every one of them. Were adrenaline and cortisol highly elevated? You can bet your hard earned, rock solid CrossFitter butt they were. You see, the high intensity exercise that we have become accustomed (addicted?!) to is perceived by our bodies as a major stressor. When wodding, we are legit in “Tiger Fleeing Mode”. This acute stress in itself is not a bad thing, as we know that stress is necessary to force positive physical adaptations (i.e. muscle growth, increases in VO2 max, positive metabolic responses). However, this stress becomes a very bad thing when it is chronic. It is a very bad thing when over-done without adequate recovery periods. It is a very bad thing when it is coupled with work problems, consistent worry or emotional stress. It is a very bad thing when our body effectively becomes stuck in fight or flight mode without at least an equal amount of time spent in “rest and recovery” mode.

Chronically elevated levels of cortisol can lead to a host of problems that will wreak havoc on your training and appearance as well as your general health. Allow me to geek out for a moment because this is important stuff if you want to be fast and strong and look hot at the lake this summer. Excessive cortisol:

  1. Inhibits insulin from shuttling glucose into cells for fuel, instead allowing an abundance of glucose to be left in the bloodstream and eventually stored in adipose (fat) tissue. READ: Excessive cortisol= no six pack.

  2. Inhibits the uptake of amino acids into muscle cells, making it impossible to properly fuel them during a workout. READ: Excessive cortisol= inadequate muscle function when lifting or wodding.

  3. Serves as an anti-diuretic which in turn causes the body to retain sodium that attracts extra water molecules. READ: Excessive cortisol= bloat and puffiness caused by water retention.

  4. Interferes with the production of thyroid hormones and conversion of T3 to T4, which play an integral role in metabolic function. READ: Excessive cortisol messes with our thyroid hormones causing excessive hunger and cravings, weight gain and sleep disturbances.

  5. Increases gastric acid production leading to digestive issues. READ: again with the bloating! Add upset stomach, excessive gassiness, constipation….

Holy crap those are some serious effects right? It is unfortunate that they directly detract from all of the hard work that we put in at the gym. Clearly we must find ways to manage the amount of stress hormones that are pumping through us every day. In truth, our systems simply cannot handle escaping from tigers over and over and over without some down time.

So if you ever find yourself overly stressed out or beat up by life, over-tired or excessively sore, DO NOT drag yourself to the box that day. Instead, consider investing your time in activities that will land you in “rest and restore” mode. Your overall health, aesthetics and progress in your CrossFit training will be better served by it.

Stay tuned for Part II, where we will discuss strategies for shutting off the sympathetic nervous system, and why margaritas sadly aren’t the solution.