Beneficial Biochemical Consequences of Excercise

When we go for a physical, doctors will often tell us to exercise more.  We all know exercise is good for us; it promotes healthy blood pressure, can help lower high cholesterol, stave off obesity, and the many associated diseases from obesity.  It can help us to fight cancer and keep the germs at bay.  But have you ever wondered why exercise is so good?  We know the positive effects of exercising, but we may not know the causes behind the benefits.

It is known that obesity leads to many diseases through a chronic low-level exposure of pro-inflammatory signals.  The fat cells themselves pump out compounds known as adipokines.  These adipokines can lead to the increased concentrations of pro-inflammatory compounds in the body such as IL-6, TNFa, and C-reactive protein.  In addition, fat cells can recruit certain immune cells that will increase the amount of inflammation.

A strong immune system is necessary for survival, however if the immune system is too strong or is always in an active state, it will lead to collateral damage within the body.  This damage can lead to several major diseases including cancer.  A consistent exercise regime coupled with a healthy diet and appropriate caloric intake will certainly limit the formation of visceral fat and will limit the infiltration of visceral fat into other parts of the body by pro-inflammatory immune cells.  In addition to limiting the amount of fat and its infiltration, exercise exerts additional benefits through the release of signals from our muscles and the body’s counter to these signals. 

All bodies try to remain in a state of balance.  Many of our biochemical pathways evolved as a response to certain conditions that knock the balance off.  In biology, many of the diseases that we experience are the result of this balance being offset in one direction versus the other.  In attempting to maintain a balance, if a tipping point is reached, the reaction can be such that there is no way to get back to the original set point; in essence the effects snowball into a condition that cannot be rescued without the addition of external help (in the form of medicine).  All medicines are designed to aid the body in reaching some set point equilibrium.  Think of a run-away train speeding down a mountain and medicine as the addition of brakes.  If the accumulation of disease signals can be stopped, and in some cases reversed by the application of a medicine, disease states will be either in remission or cured. 

When we exercise, our muscles begin to burn stored glycogen.  This results in a release of IL-6 myokine from the muscle cells themselves.  During high intensity exercise the concentration of IL-6 in the blood begins to increase and the concentration is dependent on the duration of the activity; longer and higher intensity activities will result in a larger increase of circulating IL-6.  Since this increase in IL-6 is not conducive to the body’s balanced state, it reacts by releasing compounds that counter act activities of IL-6.

IL-6 mostly acts as an alarm signal for the immune system, calling into action the big hitters.  It is normally released by cells under attack, and signals to the immune cells whose job it is to destroy pathogenic invaders.  IL-6 release is great for when a bacteria or virus is invading the body, but terrible if released unchecked during exercise.  If allowed to circulate for prolonged periods, the IL-6 released by our muscles would eventually destroy us, as the big hitters would start attacking anywhere that the signal was too high, essentially destroying us from within.

So how do we quench this release and how does it help us?  When IL-6 levels from exercise get too high in the blood, the body releases the anti-inflammatory cytokines IL-10 and IL1 receptor antagonist, as well as cortisol (a very potent anti-inflammatory compound).  The IL-10 and IL-1 receptor antagonist pathways act against the IL-6 pathways which leads to an anti-inflammatory response.  The caveat, however, is that the level of exertion must be high and prolonged in order to gain an anti-inflammatory benefit.  Thus why the relatively recent recommendation to get 1-2 hrs a day of high intensity exercise to stave off diseases caused by inflammation (such as heart disease).  The key is to reach a state where the anti-inflammatory compounds outnumber the pro-inflammatory compounds by tipping the body’s balance in the other direction.  If the anti-inflammatory compound ratio is higher than pro-inflammatory compounds, an individual will benefit from this.

So, what about people who exercise all the time, will they be super humans?  In some cases, prolonged high intensity exertion can lead to suppressed immune responses, and in turn, to the development of infections.  Remember, a body will always try to maintain a balance, and if the balance is tipped too far, as in this case from too much exercise, the negative aspects will be more infections, as the immune system is too inactive.

Therefore it is important for both sedentary and over active individuals to find their balance.  Too sedentary of a lifestyle will lead to a chronic, low-level inflammatory state and can lead to one or more of the diseases prevalent in our modern times.  Too active and it may lead to more infections.  So if you’re sedentary; go exercise! If you exercise too much; take some days off!

Since a disease state is usually the product of a balance that cannot be tipped back (without help from medicines) the key is to not let that balance get out of control in the first place.  Exercise is a simple and yet effective method to keep obesity and chronic low-level inflammation at bay, and is certainly worthwhile to anyone as potential medicine to fight many of the diseases of our modern times.