Continuous Glucose Monitoring
imperialviolet.org
imperialviolet.org
I discovered that a bunch of things I thought were reasonably healthy actually caused huge glycemic spikes -- e.g., white bread in the morning, croissants, dried mangos, excessive amount of fruits, etc.
I also discovered the importance of what you eat for your first meal in the day (either breakfast or lunch), or how to better order what you eat (fibers, fat and protein first, carbs last), light movement after eating reduces 20+ mg/dl, and more.
At this point I don't even need to wear a CGM every day; I can tell my glucose level just by thinking of what I ate earlier.
I still wear one when I'm traveling for work, as I know I'll have less control over food and calorie intake (airplane meals, restaurants, team lunches, etc).
ps: if you're interested in learning more even without using a CGM, strongly recommend "Glucose Revolution" [1].
[1] Glucose Revolution: The Life-Changing Power of Balancing Your Blood Sugar - https://www.amazon.com/Glucose-Revolution-Life-Changing-Powe...
I wonder if this amounts to optimization of an easy-to-measure and reasonably-looking but incorrect metric, much like the previous "common sense" wave of "fat makes you fat" that led several generations into a dead end.
You assume above that glycemic spikes are unhealthy which I think was never proven for the general population. Eating too much sugar or eating too much in general is bad, but I'm not aware of evidence that croissants kill you if you eat reasonably.
Another thing to note: one of the potential suspects in the obesity epidemic is HFCS, and fructose doesn't actually cause glycemic spikes. If this turns out to be true, then parallels with the "fat makes you fat" theory become uncannily strong.
I tend to think this could be the case because it matches my personal observations. I moved to France a few years ago and the amount of croissants I and people around me consume is at the stereotypes level. My weight is stable but each time I go to US for a couple of weeks I bring back 3-5 extra kilos. Something is seriously different between the food here and there, and I don't think it's glycemic spikes per se.
How exactly are they linked? Is it the size of the spike, the length, the frequency? Does it matter at all if you don't overeat? What evidence exists to support it?
For instance, the plain white rice causes a huge glycemic spike but somehow it's the US facing both obesity and type-2 diabetes wave, not Vietnam.
I agree that linking glycemic spikes with insulin resistance is "logical" but without hard evidence it's worthless and it doesn't seem to agree with the reality I see.
[0] https://cardiab.biomedcentral.com/articles/10.1186/s12933-02...
[1] https://diabetesjournals.org/care/article/38/12/2354/29088/L...
[2] https://www.sciencedirect.com/science/article/pii/S026156142...
In the absence of data my guess is that glycemic spikes simply share common root causes with health risks: overeating, junk food etc.
I say this because there's plenty of meals like white rice that cause glycemic spikes but not the health issues. And at the same time e.g fructose has low GI but seems to be linked to obesity and type 2 diabetes.
In the same way sunglasses correlate with sweating but removing the sunglasses won't make you sweat any less.
1. The excess glucose is turned into fat. This is a causal link with obesity.
2. To turn the excess glucose into fat, insuline spikes (there is also an insulin index, which can be different than the glycemic index). This is a causal link with developing diabetes (the insulin insensitivity variant).
3. The associated glycemic crash (which is very significant) causes a desire to eat more, especially more quickly digestible food. Again, a causal link with obesity.
In a relatively nutrient-poor environment the effects make complete sense: Get as much of the cheap energy providing stuff as possible and store the energy for later. In the Western world it leads to issues.
If there are issues in the "Western world" I would look elsewhere. The theory about "nutrient-poor environments" doesn't really fit the case of France which is consuming 3x more bread per capita than US while having 4x less obese people.
[1] https://pubmed.ncbi.nlm.nih.gov/34352885/
[2] https://jn.nutrition.org/article/S0022-3166(22)01097-5/fullt...
French people eat lots of bread, but it's not like American white 'bread' and it is often eaten together with plenty of cheese, olives, butter, etc. From your linked study: "Dietary carbohydrate content may not fully represent glycemic response, because other aspects of the diet, such as fat content and cooking methods, can also influence glycemic response."
Said otherwise: glycemic index != glycemic response.
> The theory about "nutrient-poor environments" doesn't really fit the case of France which is consuming 3x more bread per capita than US while having 4x less obese people.
I think you're misinterpreting. The nutrient-rich French (or American) environment doesn't cause glycemic spikes, but those spikes are problematic when they occur due to that environment. If there were only a very limited source of food in the US, the spikes wouldn't be as problematic (with regard to obesity, not insulin insensitivity).
You're just dolling up a trivial claim that excess energy causes obesity, or you're suggesting that excess energy consumption without a glucose spike (like gulping down butter) somehow wouldn't lead to obesity.
But you are right that a lot of the health problems are caused through obesity; I will not deny that.
The thing with gulping down butter is that almost nobody does that, because it quickly leads to satiety and does not trigger the desire to eat (or drink) more.
A huge confounding factor is that the same amount of calories in, holding exercise equal, may result in big swings in calories out, due to different foods' affecting metabolism differently.
Eating in a manner that didn’t cause the spikes, or at least minimized them helped tremendously with my appetite and satiety - thus being able to more successfully manage CICO.
It’s not the end-all, but it’s the number one thing I’ve found to optimize for in order to maintain a healthy calorie intake. If I’m extra careful in what I eat to avoid the spikes it’s actually somewhat difficult to eat enough to gain weight much less maintain it coupled with moderate exercise.
I live in Spain and visit the US yearly, here are my thoughts:
A) "Being on vacation" and eating / drinking a bit more loosely than I do at home.
B) Significant reduction in walking. In Spain I average 60 minutes/day on the low end, and often at 90-120 minutes/day. In the USA, it's maybe 30 minutes.
Fat does make you fat, in the sense that most of the fat in the body does come from dietary fat, but the mechanisms of this are way more nuanced than popular brochures back from "red meat kills" era would lead you to believe. Insulin itself doesn't singularly make you fat either, despite "bro science", again, there's more nuance. CICO works, but again, there's nuance to that too.
> My weight is stable but each time I go to US for a couple of weeks I bring back 3-5 extra kilos.
One thing I noticed immediately was that the bread in the US was very uncomfortably sweet, so much so that I'd put it into "pastries" category. Bought a loaf of "farmer's bread" at Trader Joe's, and while maybe not "pastry sweet", it was still in the dessert territory. Why does it take so much sugar to bake ordinary bread? I blame imperial units :-)
I'm not so sure about that? IIRC fructose is sweeter than sucrose and fructose concentrations aren't that much lower than in sucrose (fructose/glucose ratios of 42/58, 55/45, and 65/35 seem to be common from a quick search, comapred to 50/50 for sucrose). In addition the USDA also says fructose has fewer calories per gram than sucrose, which would also point towards HFCS having fewer calories per unit sweetness.
Both those would seem to point towards HFCS having fewer calories per unit sweetness, not "way more".
> white bread in the morning, croissants, dried mangos, excessive amount of fruits, etc.
white bread is basically 100% carbs (converts to sugar). croissants aren’t much better _and_ have unhealthy fat (butter). Dried mangoes pack the sugar of the fruit without much of the fiber and water (speeds up the processing of the sugar).
Healthy breakfast would be like 2 eggs with small slice of toast on the side. Or a small omelette with cheese and mushrooms and spinach. Or perhaps steel cut oats, with thin sliced banana.
Basically - real food that also not loaded with carbs and sugars. Carbs are OK if you actually need them (workouts, etc). Office workers don’t need lots of carbs.
Granted, “healthy” is a spectrum…some people would consider it a win to not smoke, drink soda, etc.
And you’re 100% right about eating fiber first. It greatly slows down sugar absorption/processing! And reduces the sugar spike. That’s an advanced tip most don’t know about.
This makes it easier to consume much larger volumes of dried mangos vs raw mangos. This basically goes for all dried fruits.
Eating three mangoes in a sitting feels like a huge amount of food. Eating three mangos worth of dried mango is pretty easy.
You can easily eat 100g of dried mango, not realizing it packs 80g of carbs (!). That's enough to create a huge glycemic spike, followed by an immediate crash half hour later.
In the end of the day, fructose and sucrose are sugars after all, so treat them accordingly.
ps: same for fruit juices. Outside of a few vitamins (which you probably don't need, if you eat a healthy diet), juices are not much better than sodas, and pack a tremendous amount of sugar.
One other thing to be aware of is dehydrated foods are less satiating (lacking water). This makes it easier to eat more of them in one sitting and consume more sugar.
So saying that it is basically 100% carbs is definitely wrong. Good wheat flour for bread has about 1/8 of its weight as proteins, while e.g. maize meal has only about 1/16 and rice between 1/16 and 1/12, but typically towards the lower end of that interval.
White bread is the cheapest source of proteins, but it has the serious disadvantages that its proteins are digested incompletely by most people and the proteins come with too much carbohydrates. The carbohydrates, i.e. the starch, can be removed totally or partially by making a dough and washing it, but that consumes a lot of water and time.
Otherwise, I agree with what you have said.
White bread could be combined with something that contains mostly proteins, possibly with fat, e.g. chicken breast or eggs, but then bread retains no advantages from its higher protein content (except of lowering the total cost of the food), so it should better be replaced by a healthier source of carbohydrates, i.e. maize or rice.
What i do know is white bread for breakfast wouldn’t be considered healthy by any nutritionist i’ve spoken to. Unless it’s paired with something else like eggs. And comparing it to cereal feels absurd, since cereal is loaded with extra sugars on purpose. Except for plain cornflakes and a few healthy brands at whole foods / trader joes.
I guess try speaking with a French nutritionist? Typical breakfast here is a "tartine" which is baguette with butter and jam. Eggs for breakfast are nonexistant. And yet very few people are fat.
The obesity epidemic is (a) very recent and (b) mostly US-specific. Something I don't understand is why people keep looking for culprits among things that are (a) very old and (b) popular worldwide.
People have been eating white bread for millenia and still do all around the world. It's unlikely that white bread suddenly became evil and decided to kill people.
Look for things that are new like sugary drinks. Or better, new AND US-specific like HFCS added everywhere including bread. Huge portions are also new and so are private cars.
I don't know what's the main driver but I'm pretty sure it's not white bread or butter.
Here is France + some other European countries + US/CAN/UK:
https://ourworldindata.org/grapher/share-of-adults-defined-a...
And here is France + other top GDP countries around the world:
https://ourworldindata.org/grapher/share-of-adults-defined-a...
I certainly wouldn’t suggest it to someone that’s already sick with diabetes or obesity for example.
I have in-laws in paris, and i will say they walk as much as NYers. In other words, they are not sedentary like most americans. Portions sizes vary a lot too.
I agree with you that sugary things that are new and trendy do a lot of damage!
Cereals have been the main sources of energy in human food for the last ten thousand years, and among them wheat (because oats is only a minor crop) has also been a non-negligible source of proteins during all this time.
I have not referred to "breakfast cereals", which are the most obvious example of garbage food provided by industrial production.
(Many decades ago, there has been a time when I was too focused on professional problems and too careless about health and nutrition, and for a long time I have been eating some Nestlé breakfast cereals. After realizing the errors of my ways and blacklisting breakfast cereals, together with other junk food, like fruit juices or fruit yogurt, I was surprised by the quick improvements brought by this decision.)
I’m in agreement!
Ha, indeed :)
I admit I was completely oblivious to what carbs, proteins, fibers, and fat do to your metabolism.
I thought controlling weight was enough. I was in the healthy BMI range, and had stopped eating added sugar a decade ago, so in my mind I was a role-model for eating "healthy". Whatever I was doing, it must be working, right?
Then my annual check-up pointed that I was entering pre-diabetic terrain...
That's what prompted me to go on a journey and discovering that it's not (just) about the weight -- what you eat matters. You need to understand what fiber/ protein/ fat/ carbs do to your metabolism, the role of insulin in controlling your blood sugar levels, that sugars are sugars, irrespective if they come in a slice of chocolate cake or a dried mango (ofc aside from fibers/vitamins), etc.
Understanding more about glycemic spikes also helped me understand about sugar crash, cravings, the sequencing of food, effect of moving after eating, and more.
I know this is all pretty obvious in hindsight, but it was a blindspot for me. It's incredible that it's not part of basic education for kids (at least it wasn't for me).
Can anyone explain how the thickness of the banana slices affects the healthiness of the meal for me?
Oatmeal by itself looks gross LOL. For me it helps to make it look more appealing. Do what works for you. Some people like putting some berries in their oatmeal or topping with some almonds.
It's delicious BTW.
Although on a perhaps more humourous note: if bread, croissants and sugary fruit is considered a healthy breakfast, I'm dying to know what GP thinks an unhealthy one is.
Small amounts of butter should not be a cause of concern, but only when butter or other dairy products are the major source of fat for someone.
As a personal anecdote, I believe that the composition of the fat one eats is very important for cardio-vascular health, because some years ago I had been diagnosed with incipient atherosclerosis.
This has scared me, so I have analyzed what unhealthy habits I might have had. At that time, I was eating very large quantities of dairy products. I could not identify anything else that was suspicious, so I have stopped eating dairy (except whey protein or milk protein, which are fat free) and I have ensured from that day on, that more than 90% of my daily intake of fats comes from a mixture of vegetable oils where oleic acid is dominant and essential fatty substances are in adequate amounts.
After a year, I no longer had any symptoms of atherosclerosis and there were also other obvious health improvements, because some signs of bad peripheral circulation, e.g. cold feet, had also vanished.
Few things in human nutrition are certain, due to the impossibility of doing experiments with humans, which could result in death or permanent health problems.
Nevertheless, it is most likely that fat should provide a good fraction of the total amount of energy, i.e. between 1/4 and 1/2, e.g. around 1/3, and the fatty acid profile should be thus that monosaturated fatty acids, i.e. mainly oleic acid, must be dominant.
Examples of food sources with fats where oleic acid is dominant are: high-oleic sunflower oil, olive oil, avocado oil, several kinds of nuts, e.g. cashew nuts, almonds, hazelnuts, pistachio, peanuts.
While such a fat with oleic acid must provide most energy, there must also be fat sources which provide essential fatty substances, e.g. linoleic acid, vitamin E, omega-3 fatty acids. (As an example of healthy daily intake, I cook my own food and most of the fat comes from the oil I mix into food after cooking, which for a day contains 50 mL of high-oleic sunflower oil or of EV olive oil + 20 mL of classic cold-pressed sunflower oil + 10 mL of cod liver oil. The cold-pressed sunflower oil is for linoleic acid and vitamin E, the cod liver oil for DHA, EPA and vitamin D.)
Healthy fats are monounsaturated and polyunsaturated fats (“unsaturated”). Found in things like nuts, olive oil, avocado oil, fish, etc.
It's baffling that those things are considered healthy in the first place - white bread, pasta, rice, potatoes contain so much starch(which is rapidly broken down into glucose) that their glycemic index is higher than that of table sugar.
Likewise, the entire reason why fruit are tasty is because they're sugar bombs. The absorption is slightly slowed by cell wall digestion, and they have antioxidants, vitamins, etc. But still. It's sugar.
> I also discovered the importance of what you eat for your first meal in the day (either breakfast or lunch), or how to better order what you eat (fibers, fat and protein first, carbs last), light movement after eating reduces 20+ mg/dl, and more.
Having read science on the topic, you're extremely right on botr counts - limiting carbs in the first meal of the day moderates glucose spikes for the entire rest of the day, and moving after high carb meals is critical because muscles uptake glucose independent of insulin signaling, massively reducing the stress on your metabolism.
Would be interesting to create some form of model of that and see how accurately you could 'guess' gliglycemia levels for a specific individual just by knowing biometric info and accurate food intake.
As in could you potentially appify your newly acquired intuition?
This feels like geek bait, imo. A nice simple metric to obsess over, and to optimise. With a super simple (therefore presumably wrong) biological model to back up it's worth.
It seems to be, that nothing particularly good has come of prior trends in quantified self-health (for regular consumers, pun intended, at least); and this seems to come packaged with a very real risk of orthorexia.
You can obsess over your glucose all you want, but if you aren't lowering your A1C then you aren't lowering your risk.
Now I would exercise and closely monitor my glucose level, then adjust my intensity when it dip lower than 100 mg/dL (5.5 mmol/L). It made the cardio exercise much more bearable, and easier to stick to it as a daily routine.
There's a reason aside from taste that sports drinks all contain a helping of glucose. I can't recall if I saw them in the US but in Europe many supermarkets offer products like "Dextro Energy", which is essentially just a sugar tablet advertised to people who need glucose during sports.
In this case, hypos will become more severe and happen easier.
Also, the store will be replenished by pulling excess glucose out of the blood over a period of roughly 24 hours after exercise or the hypo. So exercise has a beneficial effect of keeping BG lower for some time. That’s also why you should eat a little more and carbs after heavy exercise.
Taking medicines that aim at lowering the glucose level may also contribute to hypoglycemia from time to time.
When I'm working in the gym (cardio and weight lifting), I purposes train till I feel completely drained and pretty week. I'm hoping there's nothing wrong with that.
now i am running my weekly half-marathons with something sweet, and it has been awesome. Like really no big deal.
It's open source and supports all CGM sensors that I know of.
It has the ability to "broadcast" your data to various destinations and has a built-in https server to export a quick summary view to share with your doctor. It also supports exporting to Abbot LibreView so your significant others can use the LibreView app to view your data.
Don't be intimidated by the UI: it's weird and seemingly outdated, but EVERY part of the UI has a dedicated "help" button that you can click and read for details.
Couldn't be happier since I ditched the Freestyle Libre app (it failed to open after an Android update).
I suspect these devices will never go beyond 14 days at a time simply because of the glue issue. My skin was also pretty irritated once I removed the device, with some blood where the device sat.
If you chose to wear one, especially in the summer, work very hard at removing all oils from your skin before you apply it. Soap and water (preferably real soap, not SLS), and then alcohol to get everything.
I discovered that my wake/sleep cycle affected my blood sugar as much as, or even more than, what I ate.
I use an Anubis, a modified Dexcom G6, (https://www.loopandlearn.org/anubis/), which allows up to 60 days of wear. Although realistically I've never gone over 25 days. This is with adding over patches as the adhesive starts to fail though. The one I'm wearing right now is on day 18 and still doing great.
After day 10-12 I also start to do daily checks with a blood glucose meter to verify that the readings from the CGM are still correct.
The sensor chemically wears out over time too - the time limit is based on how long the manufacturer can guarantee good readings for.
I've stopped using them because it's just a bit too expensive, and my cat's diabetes is more stable now.
I opened up a freestyle libre 2, it has a EM9304 bluetooth SOC, and a TI RF430 NFC microcontroller, chatgpt deepresearch estimated the bill of materials to be about $5 USD[0].
Some companies[1] are developing reusable CGMs, the electronics are reusable, but the glucose oxidase probe, and applicator needle are still consumable. I'm not sure if that will bring the costs down much, it doesn't seem like the BOM is the main factor in the price of existing CGMs anyway.
[0]: https://chatgpt.com/share/686225c7-11ac-8005-aa4a-f420415e21...
No. A huge reason for the cost is (1) costs in R&D but also (2) the customer service/replacement requirements/etc required for medical devices.
If you were diabetic, and had a prescription for these devices, you'd be able to call Abott/Dexcom and get a replacement to a failed device shipped to you overnight. If the device didn't last the fully spec'd lifespan, you'd be eligible for replacements... etc
Another thing is that these off the shelf CGMs don't really differ in quality to their prescription only counterparts, which have a pretty extreme risk profile (patient death or hospitalization if it spits out the wrong number). They use the same parts so those costs are inherited.
I know I went from a 7.1 A1C(type 2 diabetes) to a 5.3 A1C(no diabetes) in a little over a month by going on a Keto diet while laying off the carbs and exercising regularly. If you don't CGM or not you'll end up like the almost 1/3 of the US population or 98 million Americans who are currently pre diabetic looking to join the 38.4 million who are already full blown diabetics a condition often called the silent killer for good reason (heart disease, stroke, chronic inflammation, kidney disease, nerve damage, and vision loss). Chronic inflammation also thought to have a direct link with cancer
It was impressive just how uninsightful it was, I love quantifying my workouts, my nutrient intake, etc, but the cgm added absolutely nothing.
It will change a lot of lives when some device that doesn't draw blood can continuously monitor glucose, like a smartwatch.
Non-invasive monitoring is still tricky. There’ve been some interesting attempts—like GlucoWatch back in the early 2000s, which used mild electrical currents, but caused skin irritation and never really caught on. Others have tried optical monitoring, radio waves, ultrasound, and even heat-based sensors. Feels like we’re getting closer, just not quite there yet.
I don't think they'll be as accurate as blood sensors, however they will be a game-changer for many people (pre-diabetics, or gestational diabetes etc).
Existing smart watches that claim to do this are basically garbage. Just use a random number generator instead.
Apple and Samsung are supposedly working on it: https://www.forbes.com/sites/davidphelan/2025/01/26/samsung-... But it seems to be hard and from what I have seen the new Galaxy Watch 8 won't have this feature.
Theres optical ones that can be built in a lab and require profiling to an individual. The most accurate ones are still invasive- just not consumable fungus extract based. Maybe some biomedical company makes a reference design.
I'm suggesting that it will change the world when it is an integrated part of something many/most of us buy and would eventually upgrade to.
You mean heart rate? they cleverly work by flooding your skin with the flash LED, and looking for small differences indicative of a heartbeat. Blood pressure is not something you can image with a consumer camera.
I was hugely ignorant of diabetes type 1 before my child suddenly was diagnosed with it. It's an absolute nightmare, a horrifying disease no one is taking about while there are millions of children affected by it worldwide - and the disease is spreading, getting worse every year. It's astonishing how many unknowns there are in this disease.
I've personally found my CGM to be really useful in understanding the effect of diet, sleep, stress, etc. on my blood glucose, like the OP says, but you definitely get some weird readings sometimes. Yesterday a new unit told me that my blood glucose dropped below 70 for 2 hours. It definitely didn't! After a while it got itself straightened out in time to scold me for eating some corn chips.
With the CGM there is also an additional delay of about 15 minutes in the measurements. Mostly you want to be triggered when something strange happens and then you do a manual measurement to confirm.
A false alarm of low blood sugar is annoying, but it is a lot better than collapsing. You can relax a lot more if you know you will get an alarm.
In the end though- it's still a bit of fungal extract painted onto an electrode, and an ADC that reads the value every so often. Like any other glucose monitor.
what backs this factoid?
Croissants and muffins being unhealthy should be no surprise. I am more interested in findings like food that gets a bad rap being not that unhealthy and supposedly healthy food being bad.
People also refuse to understand that juice is basically sugar water with some extra flavor, vitamins, and antioxidants that don't change how unhealthy it is for you.
White rice is basically pure carbs with barely any nutrients.
Fastfood is heavily processed but often contains enough vegetables, meat, etc to not be that bad all things told.
You should fact check your intuitions about nutrition on cronometer.com.
2 cups of cooked white rice have 17% of the days nutrients for 20% (400) of the calories (2000cal/day). 47% of the day's iron, 33% of the day's folate. 20-30% of almost every B-vitamin. 25% copper, 65% manganese, 43% selenium, 14% of the day's zinc.
Also look at 500g of boiled potato. Someone in this thread called it pure carbs. Ok, pure carbs that give you 27% of the day's nutrients for just 18% of the day's calories? That's a great deal.
I am reasonably sure carbohydrates are nutrients.
Someone chime in with what they think these might be! Should I be eating less broccoli?
It doesn't taste like it contains a lot of sugars, at least not as sweet as other desserts like a cake. But two rolls (weight wise, very small amount) would send my glucose to sky high.
Anyone know what ever happened to those?
what are you guys learning about your super special non diabetic bodies that you can't learn with a $5 book of glycemic indices or a casual afternoon reading basic diabetes dieting advice?
TL;DR:
As a healthy, non-diabetic adult I wore a Continuous Glucose Monitor (CGM) to measure my blood sugar for two weeks
The sensor was convenient to use and painless to apply, and was barely noticeable during the two weeks it was on my arm.
In analyzing my blood sugar levels, I learned a lot about my body’s response to different foods and exercise; I could identify some foods that spike my glucose.
Two weeks is too short to make detailed improvements to my nutrition in order to stabilise glucose levels — further monitor and experimentation will be needed.
Dexcom Stelo is probably the easiest to get a hold of, and the one talked about in the article too.
My father is T1 is uses the Libre CGM system for a couple years now. Libre users in the US and Europe can enjoy direct integration with their iOS devices, including constant updates and most importantly, notification alerts for dangerously high or low glucose levels, and it is even possible to share live updates of this with close family members or caretakers.
But none of this is available for my dad, as he lives in Brazil. Even though the product is same, he cannot download the iOS apps over the AppStore, as they are region locked.
Huh, never seen that typo before. Should be "remiss"
I think it is fine. It would be remiss of me to say otherwise.