NutriSense Blog

CGM Blood Glucose Experiment: 5 Insights from a Non-Diabetic

January 14, 2021
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The first time I ever put on a NutriSense continuous glucose monitor (CGM), several people questioned my purpose. "But Kara, you don’t have diabetes? But you’re young? But you’re healthy?"

My primary goal for collecting as much personalized data as I can, like the data collected from interstitial fluid-based CGM devices, is knowledge. Knowledge is power. Glucose isn't just a metric that tells you if you need diabetes management or not.

Glucose is a vital sign, just like heart rate or body temperature. It’s affected by all of your lifestyle habits, and your glucose response provides insight into your diet, fasting regimen, physical fitness, stress, sleep, and more. It provides much more than just identifying glycemic levels for people with prediabetes, type 1 diabetes or type 2 diabetes. 

Being able to see your blood glucose levels respond in real-time to all of your lifestyle factors makes it easy to identify what you're doing well and where there's room for improvement. It also helps give reason for how you may be feeling as a result of sudden drops or increases to glucose levels, or extreme levels that fall into hyperglycemia or hypoglycemia. 

Once you have access to this data, anything is possible. You can discover how your body uniquely responds to different variables. Instead of following cookie-cutter recommendations from the healthcare system, you can build a personalized routine to optimize your health. This is critical for decreasing your risk for a whole range of diseases, including diabetes, heart disease, Alzheimer's, and cancer.

As a dietitian, I am inundated with new research and nutritional information every day. Nutrition has become similar to politics with passionate ideologies and heated debates. There is so much noise in the world of nutrition, but wearing a glucose monitoring system cuts through the noise.

What's the point of wearing a continuous glucose monitor?

The initial stages of continuous glucose monitoring are all about exploration — figuring out what your baseline blood sugar levels are and how your normal routine affects those values. It provides an initial assessment of your overall metabolic health and if you suffer from conditions such as insulin resistance. Once you've gathered insights into how your body functions, you can tweak and alter your habits until everything is performing optimally. 

Since wearing CGMs (calibration can be done to match your blood tests if you have had work done previously), I've been able to fine-tune my routine based on the hundreds of data points collected by the device. There's no way I could gather this much data by just using a fingerstick. In addition to glucose readings, I've learned so much about myself in general. In this article, I'm going to share these insights so that you can hopefully takeaway inspiration for how to experiment with your own CGM and optimize your health.

Insight #1: Food pairings have a big impact on glucose levels

While wearing my CGM sensor, discoveries started to pop up all over the place. In particular, I really gained insight into my meal choices. I could list 50 different food insights I learned, but one thing that really stood out was the impact of processed foods.

Oatmeal paired with scrambled eggs is something I commonly have as a post-workout meal, and it is part of my regular routine. I have experimented with many different ways to prepare my oatmeal at this point. Altering the time of day I eat it, pairing it with various toppings, soaking it overnight, etc. Through all of my experiments, there was one variable that mattered the most — how processed the oats were.

After a lot of experimentation, I've crafted the following recipe that works best for me:

  • ½ cup oats
  • 2 tbsp of chia seeds
  • One scoop collagen
  • ½ cup of wild blueberries
  • 1 tbsp almond butter
  • Dash of cinnamon

Now, the following graph is that exact recipe, but the ½ cup of oats is instant oats:

Notice the huge glucose spike, followed by a quick return to normal blood glucose level. This response was leading to an energy crash about two hours after eating, followed by feelings of hunger an hour after that. The following graph is the same recipe, but I changed my oats to steel-cut oats. The result? A controlled glucose response and no feelings of hunger for over five hours 😎

Seeing this data helped me personalize one of my favorite foods to work with my unique metabolism.

Insight #2: A little carbohydrates can cause a giant glucose spike

I used to be scared of consuming too many carbs. I ate my oatmeal in hiding, not letting anyone know of my “guilty” pleasure. I avoided bananas like the plague. If I was craving carbs, I ate sweet potatoes, thinking they were the better alternative.

What I learned when I started measuring my food responses was the exact opposite of my initial thinking. It turns out, I can eat carbohydrates, as long as they are moderate portion sizes and coming from whole foods. It also turns out that the carbohydrate foods I thought were better for me, such as sweet potatoes, are some of my worst offenders.

As you saw above, I can tolerate steel-cut oats perfectly fine as long as I pair it with some protein and fiber. Bananas are my friend, leading to a minimal increase in glucose values. I also tolerate beans, legumes, and berries very well. And to my great surprise, starchy vegetables (including sweet potatoes) are my enemy. 

I have tried sweet potatoes in just about every form imaginable. Baked, roasted, mashed, cooled, paired with every protein or fat possible. At 7am, at 7pm. After a workout, after a walk. It didn't matter; the glucose spike will come and haunt me.

Why does this happen? 

CGM blood glucose experiment: How blood sugar levels reacts to bananas

Vs. sweet potatoes:
CGM blood glucose experiment: How blood sugar levels reacts to sweet potatoes

There could be many factors at play here, but it turns out we have a lot of variability in glucose responses between individuals. We are all a unique compilation of genetics, epigenetics, environment, and microbiomes that lead to different reactions to the same food. Research has shown that when you give a standardized meal to people, almost everyone has a widely different glucose response with a standard deviation of 31.

Everyone’s carbohydrate tolerance is unique, and that's what is so insightful about wearing a CGM — you can find out exactly where you lie on the spectrum. What I have found is that our nation’s current carbohydrate recommendation for 45–65% of calories coming from carbs is extremely high for someone whose blood glucose levels respond like mine. And that's most likely the case for a lot of other people.

About 20–25% of my calories from carbs is my personal sweet spot. If I am sick, not working out, or in the luteal phase of my menstrual cycle, I drop that percentage down to about 10–20% to compensate.

Insight #3: Late night meals increase your fasting glucose levels

Carbohydrates affect my glucose levels more negatively as the day progresses, as our insulin sensitivity naturally lowers in the evening hours. A higher glucose spike from carbohydrates consumed at night turns out to be a fairly typical response found in almost everyone.

Most of your hormones work on a circadian rhythm, and insulin is no exception. Insulin sensitivity varies from person to person. Still, most people experience the highest insulin sensitivity in the middle of the day and the least insulin sensitivity in the middle of the night.

This study showed that insulin sensitivity peaked for most people at noon, and was 54% higher than their insulin sensitivity at midnight. From an evolutionary perspective, this makes a lot of sense. Our bodies are designed to process food during daytime hours and not while we are sleeping.

I consistently found that when I consume fewer carbs at dinner and more during the daytime hours, I improved my responses to those foods, limiting glucose spikes and lowering my fasting glucose values during the night. If I decide to eat any food, especially carbs, late at night, then I will see the effect on my fasting glucose values all night long.

Take below for example — right before bed at 11:45pm, I had a bowl of popcorn. I experienced an initial glucose spike, but the real insight is what happened during the night long while I slept. Generally, if I consume popcorn during daytime hours, it will give me a small glucose spike, but then come back to normal glucose levels within two hours of eating.

When I ate it right before going to bed, my nighttime glucose values stayed elevated until I woke up the next morning. Usually, my nighttime glucose values are between 70–80 mg/dL while I sleep. Imagine if I did this every single night and had no idea this was happening! It would easily bring my average glucose up to alarming levels.

CGM blood glucose experiment: Late night snacking increase your fasting glucose levels

CGM blood glucose experiment: Late night meals elevate fasting glucose levels until the next morning

Insight #4: Glucose levels are sensitive to stress  

The most significant non-food variable that affected my glucose levels is, unsurprisingly, STRESS! While wearing the CGM, I had just started another job on top of my full-time job. I was working all the time, barely sleeping, and always stressed about finding enough time in the day to get everything done.

While this was happening, I watched my fasting glucose values consistently rise and wondered what the heck was going on. If anything, I was eating less than usual and still exercising to cope with my added stressors. After digging into the research, it became clear that elevated cortisol (the stress hormone) can drive up fasting glucose values higher than any other factor (Source)

When our cortisol levels are consistently high, this sends signals to the brain and liver that we need to make extra glucose (gluconeogenesis) and decrease our insulin sensitivity to assure that excess glucose is available to handle the stressor at hand. If this behavior is consistent over time, it dramatically increases our risk of developing chronic conditions such as type 2 diabetes (Source)

Below is a typical day for me. You can see that there is some glucose variability throughout the day. However, most of the time, I am staying between 70–100.

CGM blood glucose experiment: Blood sugar levels during a typical day (i.e. no stress)

This second picture is a day with similar food and exercise, but when my stress levels were very high. My average glucose, fasting glucose, and postprandial glucose levels are all higher due to the stress. Being able to quantify the effect that stress had on my body allowed me to realize how serious this issue was and take the necessary action to deal with it.

CGM blood glucose experiment: Increased blood sugar levels when the body is stressed

Insight #5: Seeing your glucose levels keeps mindless eating in check

Finally, and arguably most importantly, continuous glucose monitoring and receiving real-time feedback improved my relationship with food. I know I'm not alone when I admit to not always having had a healthy relationship with food.

Feeling stressed? Grab the chips. Feeling bored? Open the fridge. Binged on some cookies? Guilt and self-loathing for the next 48 hours. The amount of mental energy wasted on these silly thoughts is outstanding; imagine what I could have been doing instead.

Having real-time feedback from my body in response to my food decisions brought awareness to my behaviors. It showed the impact of my choices in a way that I can't ignore and turn a blind eye. If I ate a food I knew I shouldn't have eaten, I can see if my blood sugar levels become hyperglycemic or hypoglycemic. It held me accountable to my goals in a way that didn’t feel shameful or guilt-ridden.

I can no longer hide from my decisions or make excuses for my behaviors. Instead of going “all-out” in response to the mental stress of it all, I now have an enhanced mind-body connection that makes it easier to respect the natural signals my body gives me.

I can mindfully enjoy a treat without going overboard. I can stay on track with my goals while also freeing up mental space from thinking negatively about food. It's a gift that keeps on giving. I definitely wouldn't be able to get this type of experience just by going to my usual healthcare provider.

In summary

CGM systems enable me to optimize my health, avoid finger pricks, and become more confident in implementing very specific lifestyle changes. The beauty of personalized nutrition is that there is no one right way to eat. But, there is a better way for you to eat.

Food is a huge part of health, but there are so many other factors to consider. Is your stress unmanaged? Do you have a consistent exercise and movement routine? Is your sleep being neglected lately? Stepping back and looking at the whole picture is vital to truly understand your body and work with it instead of against it.

To figure out if a continuous glucose monitor is the right solution for you, learn about the NutriSense CGM program and subscription plans.

Written by Kara Collier, RDN, LDN, CNSC and Director of Nutrition at NutriSense.

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