Trends in glucose values are more insightful than snapshots in time.
Average values are useful for comparing behavior over similar periods.
Glycemic variability describes the “swings” in your glucose curve and gives us an idea for how certain meals or activities can affect us.
We have discussed the importance of understanding optimal fasting and post-meal glucose values, but those are only snapshots in time. What is more important is taking a step back and looking at overall trends.
You might imagine that an optimal glucose trend would be a flat line, but occasional ups and downs are normal and to be expected. Our bodies are not static and our cells require glucose to function, so there will always be some variability. What is more important is looking at the larger patterns, not each movement in isolation. Today we will cover some basic trend analysis tools to help you understand your glucose curves.
Your average glucose number is exactly what it sounds like; it is a mathematical average of all of your readings over a certain period. This single number can help us compare how we are doing from one day (or week, month) to another. A consistent increase in either the upward or downward direction of our average glucose level can illuminate either a positive or negative trend.
For example, let's say you play a sport (volleyball is my fav!) 2 days each week on top of your normal exercise and eating schedule. You may notice the average glucose on the days you play is always around 4 points lower than the other days. This comparison allows us to see that playing sports (or generally being more active) helps to lower glucose levels, and will hopefully reinforce this positive behavior.
On the opposite end of the spectrum, you may notice that a very stressful week at work (one where your sleep took a hit) resulted in an average glucose level 5 points higher than a normal week. This is a signal that lack of sleep and excess stress is negatively impacting your numbers.
Glucose Variability (GV)
Another useful tool is your glucose variability (GV) number. This number (aka Standard Deviation) describes the average size of the glucose spikes and dips over a certain period. It goes hand in hand with the Average Glucose (Mean) and tells us how far from average your glucose curve generally deflects.
Measuring GV around a specific meal or activity can help categorize it as a high variability or low variability event. For example, a meal which causes a dramatic rise in glucose, such as a candy bar might be considered a high GV food while something like an avocado would be considered fairly low GV. This allows you to make changes based on the specific responses you see to each meal or activity throughout the day.
Some variability is normal and expected, such as a decrease when sleeping or an increase during a workout. How fast and how high your glucose rises and falls is what is important. Glycemic variability serves as a great proxy for insulin production since we are not able to measure insulin levels directly.
In the example below, the top graph has high glycemic variability which can result in worse health outcomes. The bottom graph has lower variability - there are some ups and downs but the slope is gradual and the peaks are not too high.
Being able to point out the activities and food types which cause the largest spikes and dips can allow us to modify our lifestyle in such a way as to avoid these extremes and ultimately prevent the stress and damage they can put on our bodies.
To summarize the last few sessions, below are the most important glucose trends and numbers to understand. Don't forget that you can also review some of these numbers by clicking the small window icon in the upper right hand corner of your glucose graph!
Average glucose levels
Average fasting glucose levels (at least 8 hours without food)
The intensity of the “swings” throughout the day (GV)
Your highest spikes and your lowest dips
How long it takes for you to return to “baseline” values after eating