Should you wear a Continuous Glucose Monitor (CGM)?

Should healthy people use CGMs? What about people with diabetes or pre diabetes? A look at the pros and cons of CGMs in each case.

A continuous glucose monitor is a small device you can wear on your arm or belly and it measures your glucose levels continuously so you can see the change in real time after a meal for example.

I discussed CGMs with with Dr. Nicola Guess, who received her PhD from Imperial College London for work in diabetes prevention and is currently Res Program Manager at Oxford Univ where she studies approaches for diabetes remission.

In people with T2d there’s a role for CGMs. They can give immediate feedback and motivation. Always coupled with healthy diet. Be wary of exclusive focus on glucose. Just because a food flattens glucose doesn´t mean its health-promoting. Shoot for a holistic approach

With pre-diabetes: CGMs can help distinguish WHEN glucose is high. fasting vs post-prandial

For people with high fasting glucose but good post-prandia valuesl, dr. Guess mentions vigorous physical activity and high fiber diets

For people with high post-prandial glucose (after meals), emphasizing protein and moderating carbs is one approach she utilizes routinely. Amino acids stimulate the pancreas to produce more insulin which helps control postprandial glucose

For those without prediabetes or diabetes, the concern with generalized CGM use is excessive focus on glucose and the misunderstanding that glucose excursions are pernicious

It’s completely normal for glucose level to rise after a meal as long as it comes back down again. What’s unnatural is for it to stay high for a long period of time, suggesting the body struggles to process glucose normally

So it´s less about whether the CGM is good or bad and more about how we use the information.

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Animations: Even Topland @toplandmedia

References:

Disclaimer: The contents of this video are for informational purposes only and are not intended to be medical advice, diagnosis, or treatment, nor to replace medical care. The information presented herein is accurate and conforms to the available scientific evidence to the best of the author's knowledge as of the time of posting. Always seek the advice of your physician or other qualified health provider with any questions regarding any medical condition. Never disregard professional medical advice or delay seeking it because of information contained in Nutrition Made Simple!.

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0:00 What is a CGM?
0:48 CGMs for type 2 diabetics
3:25 CGMs for prediabetics
4:40 CGMs for healthy people
7:46 Glucose in endurance athletes
11:21 Summary

[x-pilot]

Summary at [11:20]

1. Is a CGM (= Continuous Glucose Monitor) useful
a) diabetics: yes
b) prediabetic: can be
c) with normal bloodsugar: not really. Real risk is cardiovascular, not glucose alone. Foods who spike glucose have other health benefits.

2. Take a holistic approach [1:50]
a) glucose level is only one part of a healthy lifestyle
b) bacon, eggs and grilled tomatoes are glucose friendly but not for cardiovascular risk, the gut microbiome, vascular function or your blood pressure
c) real risk is cardiovascular, not glucose alone [2:36]
d) glucose gets high after an intensive workout
e) glucose after eating: in a healthy person it can go up to 7, 8 millimoles per liter (= 140 mg/dl) [5:15] or even 11, 5 (= 207 mg/dl) [11:10]
- normal: a spike after 20 minutes and then goes down
- You have to worry:
* if it is still high 45 minutes after a couple of slices of bread or a small meal [10:00] -> take a test
* or if it is still high two hours after glucose tolerance test [10:35]
f) there is no evidence that having a flat glucose line after eating is desirable [6:15]
g) possible correlation between VO2 max and fasting glucose [8:30]
h) cutting carbs don't affects your fasting glucose that much [9:25]

3. GCM for somebody with T2D [11:24]
- immediate feedback
- motivation
- plus a healthy diet
- be wary of an exclusive focus on your glucose level. Because if a food flattens your curve doesn’t mean it is healthy -> take an holistic approach

4. prediabetes
Hba1c-Test can say if you have diabetes or prediabetes. But it cannot say when your bloodsugar is high [3:35], so a CGM can help you

a) if your fasting sugar is high [4:20]; [11:50]
- vigorous physical activity
- high fiber diet

b) if after a meal your glucose level stays high [4:30]
- dietary protein
- low carb

5. With normal bloodsugar

It does not really give you a health benefit.

Response from "Nutrition Made Simple!" to this question in one of the thread under this Video: "I´m not aware of a reason to base dietary decisions solely on physiological glucose oscillations (neither seek nor avoid). The concern would be the unnecessary restriction of one's diet without a clear benefit in sight. for example restricting (most) fruit or legumes only to avoid glucose oscillations is hard to justify scientifically and suggests a fear based on incorrect information from social media"

[Raherin]

I know this video is about CMG, but honestly, I REALLY appreciate the arguments about spiking glucose... there are more and more people talking about fruits being bad because of the carbs and it's bad to 'spike your glucose', it's so nice that you inadvertently talked about this! Also, it really shows how if people don't understand what's going on, they can make unwise decision because they see levels spiking. Thank you!

[raithneach]

Great video. Dr Guess is such an effective communicator, her expertise is obviously extensive but she delivers complex information in such a digestibe way.

[mrpricklypear]

So glad to see a discussion on CGM's as this exact subject has been of particular interest to me. Also glad to hear that a flat glucose line is NOT necessarily a reccomended focus as one could lose focus on the big picture.

[markotrieste]

What about CGM to detect insulin resistance? I have an A1C of 5.1, after years of low carb and intermittent fasting. However, before that, I had what I today know are symptoms of IR: huge cravings around eating hours, fainting when I'd delay a meal, BMI around 28 (now it's 24), high triglycerides and low HDL... No physician ever told me to check my insulin or glucose tolerance, I was eating way too much bread and pasta and pizza... maybe, with a CGM I could have found out earlier that I was heavily taxing my glucose physiology, despite the usual fasting glucose blood test being in the normal range.

[mikeross]

I used one in April 2021 when I was diagnosed as being pre-diabetic and I found it very useful as it showed which foods caused glucose spikes and how tweaking my diet brought my blood sugar levels back to normal.

[davidzip]

She is making some huge leaps here. I wear a CGM. But that doesn’t mean I have a glucose-centric diet. On balance, I prefer to avoid spikes, but I wouldn’t eat unhealthy foods to do so. But I might vary my routine when I am eating healthy food that spike my glucose. I might take a walk afterwards. I might make a point to eat some extra protein with the meal. She seems to be convinced that lay people can’t make intelligent choices. To suggest that someone might avoid exercise because it spikes glucose is too ludicrous to merit a response.

[Sparkling-Cyanide]

So, what’s more damaging to the body? High glucose levels or the high insulin output needed to combat glucose spikes? Also, the A1C test is low if you have bouts of hypoglycemia after eating certain foods. You end up with a falsely low A1C. I think blood glucose readings are extremely important. How else would you know if your blood sugar is still elevated after 2 to 4 hours of eating? ‘Course you don’t need a CGM to know that, just a regular meter.

Edit - I meant 2 to 4 hours AFTER eating. Not 2 to 4 hours OF eating. 😲

[alane]

I used one for about 4 weeks. It was interesting to see my glucose response to various conditions, especially exercise. I wasn’t always convinced it was accurate, so I also bought and used the typical finger poke type of monitor to compare. The CGM would often be too high or too low compared with the blood sample. The CGM would also often be sending dangerously low warnings to my phone during longer trail runs. One got down to 3.0. Since I had done that run dozens of time without passing out and since I was feeling fine, tired, but cognitively just fine, I ignored the warnings. But it was an interesting experiment. The one thing I was surprised at is the way the body pumps out glucose in the morning an hour or two before it’s time to wake up. And sometime even earlier than that.

[rn]

I would like to see some videos on how much sugar from fruit is ok to be consumed.

[justaname]

This is so interesting to listen to.
The problem is, it helps those who listen and evaluate information in a more balanced way. It probably won't help those who are already on the fear of glucose spikes ride, despite the fact that this is an expert in the field.

[chrismcgowan]

I'm not sure what the takeaway is?, there is a fear that people will misinterpret glucose spikes. I'd counter that by education not dissuading people using CGM. I myself have never used one but a person taking managment/interest in their health is always preferable to people having T2DM 10-20 years down the road. Annecdotes about extremes do little to tell us the effect on a wider scale (which hasnt been stuied yet in depth I know).
In my opinion somebody using the monitor will be much more likely to optimise other areas of their lifestyle as there is a sense of control like Dr. Guess said at the beginning. Good discussion though.

[Mojo_DK]

I am a little confused and I hope somebody can answer me. Dr. Guess says that glucose spikes are normal, and we don't know if glucose spikes are bad (they might even be helpful in some circumstances). Consistently high blood glucose is much worse.
I get all that....what I am confused about is the following:
As far as I know, one of the most basic advices is to avoid sugar and simple carbs because they spike blood glucose. One should eat whole grains because they lower glucose spikes and spread it over a longer amount of time. Why is that desirable, tho? Dr. Guess says that glucose spikes are completely normal. Whole grains lower the maximum of the blood glucose but then the time of elevated blood glucose levels is a bit longer.
Consuming whole grains is associated with health benefit, when compared to simple carbs. What is going on here?
If glucose spikes are fine, why are whole grains healthier (yeah there are some vitamins/minerals in whole grains but if that is the only difference, I am not impressed)

[scottjohnson]

Why blame the CGM for the user misinterpreting the info? Continue to educate those you believe are reacting improperly to their results and leave the CGM's alone. The info they provide can be useful for any user if they understand it. Given the huge problem we have in this country, and worldwide, with Type 2 (and the oft-related obesity et al), if a little device on arms can help people keep or get their metabolic game in order, I think it should be strongly encouraged.
Okay, I was responding to the first part of the video. Now that I've finished the rest, I see that both doctor's conclusions are, more or less, what I was saying, so NEVERMIND.

[loveandmusicpk]

Love her. This is amazing. Will help so many people who have fallen for this harmful trend.

[rn]

Excellent !!!!
Please make videos more often

[Youssef-]

Thanks for this amazing useful video .. Thanks again Gil for interviewing specialize people to give clear scientific answers away from the internet rubbish .. now i understand that spike is normal as long as you are healthy and nothing to worry about.

[TangoMasterclassCom]

Thanks, great video. Good that she mentioned the tech biohackers. They focus too much on mechanisms, and don't look at it from a holistic perspective.

[AndrewPawley]

Excellent video. Any specific thoughts on CGMs and Intermittent fasting or TRE?

[kathleenwerner]

I would love to hear this lady talk about what to do for high cholesterol.