Why We May All Wear a Continuous Glucose Monitor Soon by Mehdi Yacoubi

Why We May All Wear a Continuous Glucose Monitor Soon
Posted on
December 3, 2020

Have you ever wondered why do you feel so tired after eating certain foods?

Or why do you feel particularly energized on a given day?

There are a lot of general health principles that explain high or low energy. But it’s often hard to keep track of all of them and to make sense of a given feeling.

It would be far easier to see the exact biological reactions of our body to get a real sense of what’s going on.

It may sound futuristic, but it’s actually possible and already used by a subset of society.

People with diabetes often wear a Continuous Glucose Monitor (CGM). It consists of a plastic patch attached to a metal needle with a chip inside connected to a Bluetooth reader. CGM companies initially made these devices to help people with diabetes (Type 1 & 2) know the quantity of insulin they need to inject. On top of that, it gives your blood glucose levels 24/7 on the opposite of finger pricking devices that only give you a snapshot.

A friend of mine recently started an experiment. He got a Continuous Glucose Monitor (CGM) on the back of his triceps. He is perfectly healthy, and he does not have diabetes.

“Are you ready to see this needle get in my triceps?” he asked me on a recent Zoom call.

As I started doing my research, I found a growing community advocating for broader use of CGM, also for non-diabetics.

I was thrilled, and I wanted to know more.

I discovered there was an increasing interest in tracking personal data to monitor health and wellness. From smartwatches to sleep trackers, the trend isn’t stopping anytime soon and isn’t limited to the biohacking subculture anymore.

Right now, in most countries, you can’t buy a CGM over the counter. It’s a class II FDA-regulated medical device. It has to be prescribed by a doctor, and insurance plans cover CGM systems in most cases, a significant milestone as it usually costs more than $100 per month.

Now let’s get into the details and explore the use case of a CGM for non-diabetics.

Why knowing blood sugar is essential:

If you want to get healthier, you are usually going to leverage four main areas: exercise, nutrition, sleep, and mental health. For each of those, there are parameters you can measure and track to see whether you are on the right path or not. For example, the daily amount of steps, the number of calories consumed, or the sleep duration.

Of course, these parameters are only proxies for a goal we have. For weight loss, counting calories is often the tool of choice. However, it doesn’t take into account many variables equally as important.

The approach to becoming and staying healthy is to find good proxies to assess and measure.

Blood glucose could be an excellent proxy to monitor. Most of the parameters we usually track and leverage to get healthier don’t give us an understanding of what is going on in our bodies. What you don’t know about your blood glucose levels could be slowly wreaking havoc on your health.

When we talk about blood glucose levels, different variables are essential to consider. Mainly the fasting blood glucose and the reaction of your body after eating.

Why? Because having out of range blood sugar levels can lead to many serious diseases. For example, if you have “insulin resistance,” you may be at risk for type two diabetes, obesity, heart disease, Alzheimer’s disease, and many other conditions. No one wants to get there!

Let’s take type 2 diabetes as an example here. This chronic condition doesn’t start overnight. You aren’t going to wake up one day and discover you just got diabetic. It’s a long term process. Day after day, you deteriorate your metabolism because of what you eat and how you live.

Insulin resistance, also called prediabetes, has reached epidemic proportions worldwide. A staggering number of 50% of the US population has either diabetes or prediabetes. Most of them don’t even know it. Let alone try to fix it or manage it!

How CGMs could be helpful

CGM devices were created for diabetes. Thus, they were widely studied to assist in the treatment of diabetes. Here I’m going to explore how CGMs could be helpful in many different situations. However, let’s keep in mind this approach is more a DIY for the moment.

Assessing Prediabetes

Let’s go back to prediabetes. We are terrible at assessing prediabetes. Right now, in most countries, we rely on two tests:

  • Fasting blood glucose — one test done in the morning, when blood glucose is at the lowest
  • Hemoglobin A1C — a blood test giving an average of your blood glucose over the past three months

These two tests are missing a lot of people with prediabetes because they fail to assess how blood glucose evolves throughout the day. You could have normal average blood glucose but have very sharp spikes. They fail to give a broad view of how these levels change throughout your day. Both tests could remain normal for years while your insulin system begins to wear out.

Prediabetes shows how this device could have a significant impact on society.

According to the CDC, 40% will develop diabetes in their lifetime, so detecting prediabetes with high accuracy and optimal timing is critical. Some researchers worked on how CGMs could play a significant role in diabetes diagnosis:

The use of CGMS in the diagnosis of early dysglycemia (prediabetes) especially in high risk patients appears to be an attractive approach.

While a CGM could be a powerful tool to help detect people with prediabetes, it could do something even more significant: help everyone make sure their blood glucose is optimal, and if not, act accordingly.

For optimal health, blood glucose levels have to fall within ranges:

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American Diabetes Association

Triggering behavioral change

With this information plus a CGM, we can start to have a clear idea of whether or not our metabolism functions well. If you wear a CGM and see multiple spikes of glucose going above 140 mg/dL, you may not have diabetes yet, but you know there is something to change.

Type 2 diabetes, along with many other conditions caused by impaired insulin levels, has a strong lifestyle component. Getting to see that something in our metabolism is not going well is the first step to fixing it.

Seeing is different than knowing. Imagine you are at the airport, you buy a box of cookies, and a few minutes later you see your blood glucose level reaching 180mg/dL. The next time you’ll be waiting for your plane, you will think twice before buying these cookies, knowing how much they damage your body.

According to Dr. Peter Attia, an expert in the applied science of longevity, the most important aspect of wearing a CGM is to control behavior. Relying only on willpower to avoid junk cravings is not strong enough.Once you understand how bad these spikes are for your health, it’s much easier to resist unhealthy foods.

Lessons from wearing it

But what does it look in detail? The bigger picture of the idea is understandable, but what can I do or change to improve my health using a CGM?

Find the foods that work for you

One of the main benefits of wearing a CGM is to see how your body reacts to certain types of food. We know how bad having big spikes of blood glucose is. It’s associated with the development of chronic diseases. But it also plays a role in your daily energy levels.

We know the big principles of healthy eating: reducing sugar intake, refined carbohydrates, and so on. But we don’t see how our bodies react to what we eat.

Before trying to optimize blood glucose levels, we should first understand what is optimal. According to the most extensive study published for this subject (12,455,361 adults), the risk of death for all causes is the lowest for glucose levels between 80–94 mg/dL (Yi et al. 2017). In contrast, mortality risk increased when glucose levels were < 80 or > 100 mg/dL in both men and women:

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Association between fasting glucose and all-cause mortality according to sex and age: a prospective cohort study

For the other values of blood glucose the CGM provides, it’s hard to find guidelines for non-diabetic people as the usage of CGM is still uncommon outside of the diabetes world.

Dr. Attia suggests some guidelines for healthy people wanting to get optimal numbers:

1) Keep average glucose < 100 mg/dL
2) Keep standard deviation < 15 mg/dL (a proxy for how much insulin is needed to accomplish
3) Keep number of times I go > 140 mg/dL to a minimum

Once we have general guidelines and numbers to aim for, we can start experimenting with different variables. One of the most important is the food we eat.

A few years ago, a study was published where researchers gave 800 participants different sources of carbohydrate-rich foods while having their blood glucose levels monitored. What they found is alarming.

The paper showed that people respond with a large variability to the same meal. For example, participant 663 (chart E) had a more significant blood sugar rise for bread than for pure glucose, and participant 468 had the opposite, which is what we would expect.

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High Interpersonal Variability in the Postprandial Glycemic Response to the Same Meal

The researchers also studied the response to the same amount of carbohydrate (50g) from different sources of food (chart G). Here again, the difference between individuals is striking. While participant 644 had a good glucose response to banana and not cookies, participant 445 had the opposite!

So what does that mean? Unfortunately for us, it doesn’t mean cookies are healthy, nor are they healthier than bananas. It does mean, however, the response to the same type of food can vary dramatically from one person to the other. The general guidelines are obsolete because they fail to assess the variability between individuals.

Right now, regarding diabetes, science classifies people in 3 categories: non-diabetic, prediabetic, and diabetic. But as we just saw, people have a completely different response to the same food. It bears the question of why are we only categorizing people in 3 groups. A group of researchers at Stanford tried to translate this phenomenon by introducing different “glucotypes.”

Here, we continuously monitored week-long glucose levels in an 800-person cohort, measured responses to 46,898 meals, and found high variability in the response to identical meals, suggesting that universal dietary recommendations may have limited utility.

For example, the glycemic index isn’t useful because, on top of inter-personal variability, you rarely eat the foods by themselves. White rice has an index of 74. But what’s the index of white rice with olive oil? Adding fat sources to carbohydrates is often said to reduce the glycemic load of the meal. But without knowing how your body responds, you can’t take action.

Bottom line, even if you are eating supposedly healthy, you could be slowly but steadily damaging your metabolism. After doing a lot of research on this topic, I decided to track my blood glucose with a CGM for a month.At the time I’m writing this, I just had the CGM for about a week, and I am already blown away with what I saw.

The first shock came from breaking a fast with oatmeal & banana pancakes. It skyrocketed my blood glucose to 194mg/dL. Right now, I am doing many more experiments, and I will write a full piece on it in the coming weeks on how I managed to find the foods that work for and the ones that don’t.

Damage control

It’s not just what you eat, but it’s the physiologic state you are in when you eat it.

It’s a very different glycemic response if you eat a bowl of pasta after you’ve exercised intensely for 30 minutes versus eating it after having not having exercised.

In the chapter “The glucose switch” of his book “The 4 Hour Body”, self-experimenter Tim Ferriss shows how he managed to improve his blood glucose levels. He went from bad (a lot of spikes going above 140mg/dL) to mostly flat by using a few techniques he describes in the book (increasing the amount of fat in every meal, exercise, meal timing, speed of eating among others, etc.).

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These two graphs show food quality may be only one variable among many others to consider. After implementing his techniques, Tim managed to flatten his blood glucose (graph on the right) while still eating unhealthy foods (chocolate croissants, almond croissants).

Knowledge is power

Once we understand how our body reacts to various foods, we can learn from our mistakes and our successes. We just saw how diet could impact us. But other factors play a huge role.

Stress levels are a significant parameter to take into consideration. For example, fasting blood glucose upon waking up should be below 100mg/dL. But with elevated morning stress, you could find a value above 100mg/dL while having been stable and under 100mg/dL for the whole night. Intense exercise also spikes my blood glucose, for example.

By tracking these parameters, at least for a few weeks, you can start noticing patterns. You may understand why the afternoon slumps hit you every day at 3 p.m, or why you were so energetic on your Monday workout and so tired on Friday. It can have a dramatic impact on your everyday performance.

A CGM doesn’t lie. It gives honest, fast, and reliable feedback about your diet. As humans, we are feedback machines, and CGMs help you understand whether your lifestyle is good and if the changes you’re making are going in the right direction. It holds you accountable. Blood glucose levels can improve very fast when you make the right changes, which is an authoritative source of motivation.

Feedback is power, but it comes with its limits.


A CGM can be a powerful tool to help you assess and improve your health, but some challenges remain before massive adoption.

Obsessing over the numbers

At first, it’s easy to get obsessed with the number on the CGM. After checking with other people who wore one, I understood it’s a typical pattern. There is something addictive to checking the numbers all day long. After eating this, during exercise, you name it.

Obsessing over it may come from the nature itself of the experiment. The sole fact of tracking and the stress it may induce can impact your body. There haven’t been studies about this, but I noticed, at least personally, that the fear of getting an out-of-range number may very much be the reason for this number.

It can be hard to find the right balance between too much tracking and obsessing and not caring at all. It’s not a problem specific to health optimization but a broader one: what level of tracking/experimenting will enable harmony and real optimization? Because if you freak out and obsess over the little details, it may (or may not) help you fix your blood glucose, but it could jeopardize other aspects important in your balanced existence (mental health, relationships).

Knowing your favorite meal is spiking your blood glucose like crazy or that your tolerance to carbohydrates is far lower than expected may be very useful. Still, it can also be complicated news to process. Again it’s all about finding the right balance for you.

Not getting actionable insights

I thought it would be easy to find precise and actionable information about blood glucose readings for non-diabetic people. I was wrong.

For now, wearing a CGM as a non-diabetic is a demanding project. Most of the information out there is for people living with diabetes. It’s particularly hard to know if your blood glucose levels are optimal, and if you see something weird, it’s even harder to tell if it’s the “don’t worry about it” type of weird, or the “Mmh, you should get that checked” kind of weird.

Even to find the foods that work for you, it requires a lot of attention in tracking and analyzing the data. I guess that it will become more comfortable in the years to come as these devices go mainstream. But for the moment, it takes time and effort.

For CGMs to be useful, companies need to make software improvements to help analyze the patterns in your life and make recommendations for your diet and lifestyle.


According to the latest trends, the self-quantification movement applied to health optimization isn’t stopping anytime soon. Promoting a prevention-based approach to health is the way to go, especially for preventable diseases (metabolic syndrome, type 2 diabetes). But a few points are still hindering the extensive usage of these technologies, mainly science-based actionable insights and the alignment of economic incentives.

A need for more studies

For CGM usage, we need more studies exploring their use case for non-diabetic people. Science is still emerging; we have a lot to learn for intra-person variability and inter-person variability.

Right now, all evidence is anecdotal; we need a robust analytics system to get a sense of the data. Even if the logic behind using more extensively CGMs makes sense from a scientific standpoint, there are no proven benefits of wearing it in the long term for non-diabetics. Short-term usage may prove its benefits soon.

Another area where blood glucose management could be of paramount importance is for Alzheimer’s disease. Recently researchers proposed the term ‘Type-3-Diabetes’ for Alzheimer’s disease (AD) because of the shared molecular and cellular features among Type-1-Diabetes, Type-2-Diabetes, and insulin resistance associated with memory deficits and cognitive decline in elderly individuals. If it’s confirmed and more papers draw the same link, blood glucose management may take even greater importance in disease prevention.

Legal landscape

CGMs are a regulated medical device in most countries. The main reason is that they can give a precise amount of insulin to inject for diabetic patients, and regulatory authorities don’t want this information used outside of the doctor-patient relationship. For more extensive use of CGMs, they will first have to be legal, and for that, there are two options. Either the ones for non-diabetic people will be less accurate (values given in ranges or non-real-time), or they are going to be more easily prescribed by doctors outside of diabetes.

If not covered by your insurance plan, this little experiment can get costly!

Alinement of the incentives

Because of our financial world, even if something makes medical sense, if it doesn’t make economic sense, it won’t get a massive adoption. That’s currently the big problem of a prevention-focused approach to healthcare. We all understand that investing money in preventing diseases later will be beneficial economically. But it’s still tough to prove it to the payers. The problem often comes down to misaligned incentives (especially when there isn’t a single-payer system that would benefit from any cost cut).

Most insurance companies have a short-term outlook, and when it comes to prevention, here’s how they would think:

  • A 25-year-old isn’t generating complications yet.
  • And a 25-year-old is with an insurance plan for a few years before they move to their next job, and they’re on another insurance plan for a few years.
  • In other words, the insurance company doesn’t care if they get sick in 30 years; they only care about the next couple of years.

According to Kevin Sayer, CEO of Dexcom:

“We have to do a better job as a company documenting these economic benefits.”

And so do the other companies promoting prevention as a cost-saving and health optimizing alternative.

I see CGM systems as a massive opportunity for preventive medicine, let’s hope they become widely available and more easily insightful soon!

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