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

Kara Collier, RDN, LDN, CNSC

Published in CGMs and Sensors

10 min read

November 13, 2020
May 23, 2023
someone looking at their glucose data in the Nutrisense app
someone looking at their glucose data in the Nutrisense app

The first time I ever put on a 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 helps guide diabetes management. In fact, there are a number of reasons that using a CGM without diabetes can be beneficial for making healthier lifestyle choices.

Glucose is a vital sign, just like heart rate or body temperature. It may be impacted by your lifestyle habits, including your diet, fasting regimen, physical fitness, stress, sleep, and more. Glucose patterns may provide much more than just identifying glycemic levels for people with prediabetes, type 1 diabetes or type 2 diabetes. 

What's The Point of Wearing a Continuous Glucose Monitor?

Being able to see how your blood glucose levels respond in real-time to your many lifestyle factors makes it easy to identify what you're doing well and where there's room for improvement. It also may offer some insight into certain symptom patterns such as post-meal fatigue.

Once you have access to this data, you have more power. 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.

Customizing your diet and lifestyle habits to fit your body's needs can help you reduce the risk of future health concerns, and conditions like cardiovascular disease, diabetes, 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 can help cut through the noise.

Getting Started with a CGM

The initial experience of wearing a continuous glucose monitor is all about exploration — figuring out what your baseline glucose levels as a non-diabetic are and how your normal routine affects those values. It provides an initial view of how your current approach may be impacting your glucose levels.

Once you've gathered insights into how your body functions, you can tweak and alter your habits accordingly over time. 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, and that's one of the many benefits of the CGM device. 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 take away inspiration for how to experiment with your own CGM and support 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 heavily 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 CGM 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 tablespoon of chia seeds
  • One scoop collagen
  • ½ cup of wild blueberries
  • 1 tablespoon almond butter
  • Dash of cinnamon

Now, the following CGM graph shows what happened when I ate that exact recipe around 8 a.m. with instant oats:

glucose response after eating instant oatmeal
Kara's mid-morning glucose spike after eating a bowl of instant oats. The orange line signifies that her blood sugar levels surpassed 140 mg/dL.

Here, you can see what is considered a glucose spike occurring around 10 a.m. Notice this huge glucose spike, followed by a quick return to normal blood glucose level a few hours later. This response led to an energy crash, 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 and consumed them around 7 a.m. The result? A controlled glucose response and no feelings of hunger for over five hours.

a graph of glucose levels after eating steel cut oatmeal
Kara's glucose response after eating a bowl of steel-cut oats at the same time of day. Here, her mid-morning glucose levels didn't surpass 120 mg/dL - a huge improvement.

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

Insight #2: A Few 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 personal glucose 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 7 a.m., at 7 p.m., or after a workout, after a walk. It didn't matter; the glucose spike was inevitable.

Why does this happen? Just look at the difference between bananas and sweet potatoes on two different days after I ate each of these foods around noon:

glucose response with bananas and sweet potatoes
Kara's glucose response after eating a banana vs. eating a sweet potato around noon each day. The sweet potato led to a glucose spike of more than 140 mg/dL, while the banana had minimal impact.

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, 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.

About 20 to 25 percent 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 to 20 percent to compensate.

Insight #3: Late Night Meals May Increase Your Fasting Glucose Levels

Carbohydrates affect my glucose levels more negatively as the day progresses, as 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 many people.

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 percent 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.

glucose after eating popcorn
Kara's glucose response after eating popcorn before bed. In the second graph, her glucose spiked above 140 mg/dL between 12am - 4am while she slept.

When I ate it right before going to bed, you can see that 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.

Now, imagine if I did this every single night and had no idea this was happening! It could easily bring my average glucose up to alarming levels.

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.
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 ensure 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. Below is a normal CGM graph on 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 70–120 mg/dL.

glucose graph with and without stress
Kara's glucose response on a low-stress vs. high-stress day. Even when eating similar foods, her glucose response was significantly impacted by her high stress levels on the second day, causing a lot of variability.

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.

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, my blood sugar levels become hyperglycemic or hypoglycemic. I could also feel a difference in my symptoms, like energy levels.

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.

Now, through the benefit of continuous glucose monitoring, 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 from just any healthcare resource out there.

As you can see, there are many different factors that can cause your glucose levels to vary—and everyone's response may be different. If you’re ready to unlock your body’s unique data and start achieving your health goals, the Nutrisense program is here to help. See how Nutrisense can support you in creating healthy lifestyle habits and optimizing your well-being today.

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Engage with Your Blood Glucose Levels with Nutrisense

Your blood sugar levels can significantly impact how your body feels and functions. That’s why stable blood glucose levels can be an important factor in supporting overall wellbeing.

With Nutrisense, you’ll be able to track your blood glucose levels over time using a CGM, so you can make lifestyle choices that support healthy living.

When you join the Nutrisense CGM program, our team of credentialed dietitians and nutritionists are available for additional support and guidance to help you reach your goals.

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Heather Davis, MS, RDN, LDN

Reviewed by: Heather Davis, MS, RDN, LDN

Heather is a Registered and Licensed Dietitian Nutritionist (RDN, LDN), subject matter expert, and technical writer, with a master's degree in nutrition science from Bastyr University. She has a specialty in neuroendocrinology and has been working in the field of nutrition—including nutrition research, education, medical writing, and clinical integrative and functional nutrition—for over 15 years.

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