I Tried a Continuous Glucose Monitor for a Month. Here’s What I Learned
How wearable technology can revolutionize diet and health
After learning about the harms of ultra-processed food, I switched my diet to real, whole foods. I thought that if I shopped on the perimeter of the grocery store and ate what my great-grandmother considered food, I would stay healthy. Little did I know that I was putting a halo around all real food without understanding my unique metabolism, or how my body breaks down food for energy.
Metabolic health is the cornerstone of healthy minds and bodies. At least 88 percent of Americans are metabolically unhealthy, measured by blood glucose, triglycerides, HDL cholesterol, blood pressure, and waist circumference. Metabolic dysfunction sets people up for a host of chronic diseases, ranging from Type II diabetes to heart disease and cancer.
Before now, we didn’t have a simple way to monitor metabolic health and tackle problems before disease sets in (which can take years, even decades). Enter the continuous glucose monitor (CGM), a wearable biosensor that is revolutionizing metabolic health by showing how blood sugar responds to food and lifestyle choices in real time.
The goal is to keep glucose curves relatively stable and avoid repeated spikes and dips — also known as the blood sugar roller coaster. In the short term, these highs and lows can lead to cravings, weight gain, fatigue, mood swings and sleep difficulties. In the long term, they can cause insulin resistance, fatty liver disease, depression, infertility, dementia and more.
Why the far-reaching effects? Because the human body is fueled by trillions of mitochondria, powerhouses of the cell. When mitochondria get overloaded by, say, excess glucose, they can’t produce energy as efficiently. Over time, this can lead to damage in all parts of the body.
“I don’t want people to think they have hypertension, elevated cholesterol, type 2 diabetes. They have one problem, really, with a root cause: mitochondrial health,” Dr. Howard Luks told GQ earlier this year.
Glucose spikes can even accelerate aging by increasing oxidative stress, inflammation and glycation. “The more often we spike, the faster we age,” Jessie Inchauspé writes in Glucose Revolution.
The Procedure
I recently had the opportunity to try the Freestyle Libre 2, a continuous glucose monitor that offers a free 14-day trial. The CGM sits on my upper arm and collects glucose data from the interstitial fluid right below my skin. The tiny device stores data for eight hours and sends it to my smartphone with a simple scan. My phone then displays the glucose curve on an easy-to-read graph. I can see the effects of food, exercise, sleep and stress on my blood sugar — all of which can be tracked in the app.
I was a little worried about installing the CGM because a tiny needle is involved. However, the application was fast, easy and didn’t hurt at all. The device stays on for two weeks — and trust me, the adhesive really sticks. I started using the CGM in Florida, where I spent two weeks swimming in the pool and even in the ocean (the device is water resistant for 30 minutes). I was nervous that it would come off, but it stayed strong. Sleeping on the CGM was also not a problem, though I don’t recommend bumping into walls.
What did I gain from my personal science experiment? I learned that I could have large glucose spikes eating some of my favorite “healthy” foods. Let me explain.
The Results
While I eat some animal protein, I mainly eat plants. I like plants. If I could eat plants all day and be healthy, I would. However, I learned years ago that my body needs some high-quality animal protein. I eat eggs most mornings and meat a few times a week, preferably pasture-raised. However, the majority of my meals still center around plant-based proteins like quinoa, lentils and beans.
While I had a slight feeling that these plant-based proteins might not be ideal for me, I carried on for years eating lentil soup almost every day. Quinoa was my best friend (I mean, it’s a complete protein, it must be healthy). Sweet potatoes were also a mainstay in my diet, a “better choice” than white potatoes. Let’s just say that I was in for a rude awakening when I saw my glucose curves.
Before we proceed, a quick caveat: Everyone is different. I am not making conclusions about which foods are healthy or not based on my glucose experiments. I am merely reporting my results and personal conclusions. I highly recommend doing your own investigations to find out which foods are right for you.
We know that refined carbohydrates — like cookies, rice and bread — can cause massive glucose spikes. They contain little fiber, which slows the absorption of glucose (and fructose*) into the bloodstream. When glucose rises, the pancreas releases insulin to bring blood sugar back down to a safe range. As glucose falls, we might experience fatigue, cravings or irritability and reach for more carbs. Hence, the blood sugar roller coaster continues.
Sometimes, the pancreas releases too much insulin in response to carb overload. This can cause low blood sugar or hypoglycemia, which triggers the body’s stress response. A host of mental and physical health symptoms can ensue, which are often misdiagnosed for years.
*Note: Sucrose, the sweet molecule, contains glucose and fructose. Glucose can be metabolized by all cells, but fructose can only be processed by the liver. While fructose doesn’t show up on the CGM, it can wreak even more havoc on health than glucose alone. When we eat sweet foods, we can picture an invisible fructose curve alongside our glucose curve — and yes, we also want to keep it down. To learn more about fructose, check out Dr. Robert Lustig’s work. His famous lecture, Sugar: The Bitter Truth, has hit 22 million views!
Complex carbohydrates contain more fiber than simple carbs. They supposedly digest slower and lead to lower glucose spikes. However, I had some major glucose spikes from complex carbohydrates like quinoa and sweet potatoes.
I am now going to show you zoomed-in graphs from my Freestyle Libre App. *Please note: these graphs are just for illustrative purposes. I know they don’t have proper axes, labels, etc. Their purpose is simply to provide a general idea of what glucose spikes look like. Data geeks, please lower your weapons.
Here is my spike from eating lentil soup packed with mushrooms, carrots, celery and sweet potatoes.
For reference, an optimal post-meal glucose spike is less than 30 points according to Levels Health. My target glucose range (green shading) is based on Levels’ proposed range: 72–110. This is a tighter range than current recommendations, which Levels found to be too lenient for optimal health.
The lentil soup caused a whopping 60 point spike. I think the sweet potatoes did me in, as I even spiked from sweet potatoes in beef soup (though not as much). Lentil soup is a mainstay in my diet, so I tried ditching the sweet potatoes and adding cabbage instead. Here’s what happened:
Woohoo — in range! Granted, when I ate the same soup for lunch the next day, the spike was nearly double (though that’s still half of the spike from the sweet potato version). Glucose responses are dynamic — they vary based on time of day, stress, sleep, exercise and other factors.
Before moving on, let’s take a look at another spike on this graph. Research shows that we can lower glucose spikes by eating carbohydrates after vegetables, protein and fat. In other words, carbs go last. Here, I ate green beans and eggplant with tahini, followed by red beans.
Eating beans after vegetables and tahini still resulted in a spike, but it was a much lower spike than when I ate rice and beans the week before. Seeing the improvement makes it easy for me to ditch the rice!
Next up we have my favorite plant-based protein, boasting all nine essential amino acids and enough carbs to send my glucose soaring: quinoa.
Here, the quinoa was warm and mixed with cooked vegetables. When I ate the quinoa cold for lunch the next day in a salad, the spike was about half (research shows that cooling starches can help reduce spikes). Overall, I found that the less quinoa I have in salads and more protein, fat and vegetables, the better my glucose fares.
Fruit was another big surprise for me. I knew that modern fruit is bred to be bigger and sweeter than nature intended. Still, I thought the fiber content would be enough to slow sugar absorption because it forms a gelatinous barrier along the gut. That’s why whole fruits are better choices than fruit juice or smoothies, where the fiber is removed or obliterated. However, whole fruit still caused big spikes for me.
Here is a peach I ate with a handful of pumpkin seeds (research shows that eating carbs with protein or fat can lower spikes).
The pumpkin seeds obviously weren’t enough to mitigate this spike. I was determined to find a glucose-friendly way to eat fruit. Below, I was able to stay (mostly) within my target range by combining fruit with more fat, protein and cinnamon, all of which have glucose-lowering properties.
Still, I was surprised how much fruit affects my glucose levels. In that first spike, I only ate half a date! Jessie Inchauspé, founder of Glucose Goddess, debunked the myth that dates are good for diabetics and overall blood sugar. Check out her graphs here.
Lastly, here is what a glucose curve looks like from a low-carb breakfast. Research shows that keeping glucose low (and protein high) early in the day can increase energy levels all day long.
Conclusions
Overall, I am so grateful for the opportunity to peek inside my biology to see how I react to my regular diet. I’m not trying to demonize plant-based proteins, complex carbohydrates or fruit. I just want to show the effects they can have on glucose levels so we can make smart decisions if we choose to eat them.
Luckily, there are many hacks that can lower glycemic response, such as eating fiber, fat and protein before carbohydrates. Taking a walk after a meal can also help, even if it’s only for a few minutes. Meditating, or reducing stress, can also have immediate effects on reducing blood sugar.
Check out more glucose-lowering hacks in Jessie Inchauspé’s book Glucose Revolution or her social media accounts (@glucosegoddess). Levels Health is also a great resource for CGM and metabolic health content.
Lastly, if you’re interested in trying a CGM, consider the free 14-day free trial from Freestyle Libre (no, I don’t work for them—I just think it’s an unbeatable opportunity). You’ll discover your unique blood sugar response to food, as well as sleep, stress and exercise. Remember, it’s just data. There’s no pressure to make any lifestyle changes before you are ready. Knowledge is power — and it’s a lot of fun too!
