Exercise, body fat, and sugar: how these three work together to fuel our busy lives:
As a species we took an evolutionary gamble in the early days of our existence. We developed an organ more complex than any other species, our brain. The gamble came from the fact that this amazing organ needed a constant uninterrupted fuel supply in the form of sugar (glucose) in order for it to function to its full potential. More than ten thousand years ago, before we began cultivating our own crops and domesticating animals and their products for food, our ancestors may have gone days without having a hearty meal. For this reason our bodies evolved and developed the ability to store sugars effectively whenever it was available.
Humans can store sugar â€˜glucoseâ€™ in three different places. Most of this glucose (~80%) is stored in our muscles in the form of â€˜glycogenâ€™ which supplies us with the necessary fuel to power our muscular contractions. Our blood holds ~6% of glucose, usually referred to as â€˜blood sugarâ€™. The levels of our blood sugars vary throughout the day and are heavily dependant on our diet. The final 14% of our total body glucose is stored in the liver as glycogen.
Fast forward to 2015 and one could argue that we (human beings) have yet to adapt to the change in our society where food is in such abundance. Our brains, at least from an evolutionary standpoint, still havenâ€™t adjusted to the fact that there is a fridge in our kitchen that can re-fill our energy stores when needed. Combine that with a chronically high dietary carb intake and what you get is overflowing glycogen reserves in your liver and muscle tissue. Since thereâ€™s nowhere to store this excess glycogen, our bodies have no choice but to convert it to body fat.
The brain works with another important organ, our pancreas, in order to detect how much glucose we get after we eat something. The pancreas responds by releasing a chemical message, a hormone, called insulin. Insulinâ€™s message to the cells is â€œabsorb sugar and store it! Suck it up out of the blood and fill our glycogen stores!â€ This process regulates how we keep a steady balance between stored glycogen in the â€˜reserve tanksâ€™, and circulating levels in the blood stream. Problems arise with this process when we already have full reserve tanks and too much sugar in our bloodstream.
When glycogen reserves are completely filled, our blood sugar stays elevated. When our brain detects high blood sugar it releases even more insulin in order to drop it back to down to a normal level. Over time if this process continues, we develop a resistance to insulin. Its message to the cells isnâ€™t being heard.Â As a result, the pancreas creates more insulin since now it has to be released in much higher concentrations in order to keep blood sugars balanced. This puts a major stress on our body, particularly the pancreas. It is possible to burn out our pancreases to the point where it can no longer respond to such a high demand for insulin. Our bodies then loose the ability to respond and regulate blood sugar levels. This is what happens to people who develop type 2 diabetes.
There is good news. Exercise can help with blood sugar regulationâ€¦but how?
As we mentioned earlier, sugar is stored in all of our muscles in the form of glycogen. When we begin to perform muscular contractions, like when we lift weights, the energy within that sugar is broken down to fuel our working muscles. The more work that is performed, and the greater the intensity of said work, the greater the amount of glycogen that is broken down and depleted from our muscles (translation: work harder, burn more sugar). The effect of this has great benefits to our resting blood sugars and our metabolism.
Following a hard bout of exercise, our glycogen tanks need to be re-filled. This process initiates an almost reverse reaction to what happens when we eat sugars. When we diminish our reserve tanks, our muscles and liver will absorb sugar from our blood in order to re-fill them. When this happens, it leads to a lower blood sugar, which our brain detects and in turn initiates the process of getting it back up to a more comfortable level. After a workout our muscles are now more sensitive to the hormone insulin (our storing hormone) so sugars available in the blood will be soaked up by those muscles instead of those sugars getting shunted towards fat cells for storage.
If we sustain this practice of routinely emptying our energy reserves (via challenging resistance training), we give our bodies and our pancreas a break from having to constantly produce high amounts of insulin. When insulin isnâ€™t constantly circulating in such high concentrations, it makes it easier for our bodies to start to burn fat. It sets us up internally to be in a fat burning state, as opposed to constantly trying to store store store! Aside from just weight loss, improving your insulin resistance and glucose management can lead to improvements in cardiovascular health, metabolic health, and cognitive function as well.
Regular resistance training, with a significant level of effort is crucial to ensure you are managing your blood sugars properly. It is an essential piece in improving your metabolism and body composition. If you are looking for significant body composition changes, a proper nutrition plan will be necessary.
Thank you for reading!
Evan Snow, B.Sc.Kin, Personal Fitness Coach