Individualization of Glucose Metabolism (CGM)

In the last post, I discussed the fact that carbohydrate intake and glucose metabolism are both crucial for optimal health and performance.  Diet and exercise both impact this interplay of sugar and insulin, but there is individual variation that dictates what may be best for you.  A lifetime of diet and exercise habits, coupled with genetic and epigenetic influences create a unique environment in your body.  Generic recommendations can be fine, but if you want better than that, it is important to discover your own personal physiology.  This used to be a difficult and expensive task, but new technology has made this process much more accessible.

Continuous Glucose Monitoring (CGM) has become readily available in forms which do not impede your day to day activity.  At Podium Sports Medicine, we offer the Abbott Freestyle Libre system to our patients.  This allow you to wear a small sensor on the back of your arm while you work, swim, bike, run, eat, and sleep.  You get data 24/7, which we can then correlate with your training and diet to give you personalized recommendations.

To give you an idea of how such information can be gathered and utilized, I’ll tell you a bit about my personal experience using CGM.

The Freestyle Libre sensor is about the size of a quarter.  I placed one on the back of my arm and wore it for 10 days.  It has a maximum utility of 14 days, but you can get reasonable data in as few as 3-4 days.  The sensor has a small catheter that stays just below the skin, constantly measuring and recording blood sugar levels.  The data cannot be immediately viewed by the patient, but once downloaded, it is easy to review and analyze glucose levels and trends.  Surprisingly, it was entirely painless to place the sensor.  I thought there’d be a small sting or pinch, but you really can’t feel it at all.

When I downloaded my data and compared it to my diet, training, and sleep logs, some interesting things presented themselves.  Some of it I would not have expected!

My diet directly impacted my blood sugar levels in many situations, but not all.  I generally eat a moderate amount of carbohydrate (125 - 300 grams per day, depending on activity level).  I have, in the past, measured my blood sugar and ketone levels upon waking.  I have developed a diet that keeps my blood sugar appropriately low through the morning hours.  Interestingly (to me), there were some afternoons where my levels were much higher than I’d desire or suspect.  This could be traced to both dietary choices and stress.  Also of interest, there were times when I would splurge dietarily but see little to no increase in my blood sugar.  This relative immunity was again due to stress (or the lack thereof) and exercise.

Stress leads to secretion of cortisol, a hormone which signals the liver to release stored glycogen and cause an increase in blood sugar.  From an evolutionary standpoint, this helps fuel your escape from the wooly mammoth that is threatening to eat you.  (Unless wooly mammoth were vegetarian…I have no idea.)  When stressed at your desk though, the sudden rise in blood sugar (and subsequently, insulin) are more likely to be harmful than life-saving.  Seeing this process objectively with CGM made me realize how necessary it is to mediate such stress.  As with most such stressors, it also made me realize how trivial most of these issues were…certainly not worthy of risking my health!

In addition to the impact of stress on blood sugar, I learned that lack of sleep can be a major health detriment in this regard.  I remember years of medical training when I averaged 4-5 hours of sleep per night, if I slept at all.  Since that time, I’ve seen the studies that show that a single night of sleeplessness can render a non-diabetic person as insulin resistant as a Type II diabetic.  Intellectually, I understood the link, but it’s hard to appreciate damage that you can’t see.  Using CGM though, I saw near-diabetic blood sugar levels in myself on days after I slept only 5 or 6 hours.  It was shocking to me!  After sleeping 5 hours one night, my sugar jumped to inappropriately high and remained that way for too long.  And I’ve seen this repeat itself in numerous patients as we’ve been offering this service.  While you may argue that you can function on 5 or 6 hours of sleep, it’s hard to say that’s “healthy” when your glucose metabolism is so dysregulated.

CGM readings after too little sleep.

CGM readings after too little sleep.

CGM monitoring can offer you an objective and individualized insight into how your body reacts to your diet, stress, and sleep patterns.  Without gathering such information, you can make educated guesses, but I’ve found that those can be rather inaccurate.  Sure, they can be useful, but it is nearly impossible to optimize your health and performance on conjecture alone.  As a corollary, you could go out on the bike and train “by feel” for 3-4 hours every day, but you will get much fitter and faster if you use a power meter and target your training.

Speaking of training, the final post in this CGM series will look at how glucose metabolism is impacted by exercise.  This is the good stuff!  Stay tuned…


At Podium Sports Medicine, we’ve put together a package to help you assess your individual glucose metabolism and make personalized recommendations on improving your health and performance.  This is a great tool for both diabetic and non-diabetic patients, regardless of your athletic or wellness goals.