Continuous Glucose Monitoring

I've been using a CGM on and off for the last year, and it has given me a whole new perspective about food and nutrition.

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 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 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.

> 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.

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?

The difference is corn syrup (in everything) vs sugar from sugar beets. Corn syrup has way more calories por unit sweetness.

I only casually follow these things, but my understanding is that interest in glycemic spikes is not really about obesity or fat at all, but more about diabetes-related issues, insulin resistance I think.

> 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.

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.

Large glycemic spikes are are an issue, but the problem is not obesity. Obesity is concerned with calories in and calories out and our current obesity epidemic is largely attributed to the fact that we eat more calories and move less. Most other discussion points are secondary to that fact. Glycemic spikes on the other hand are linked to increased insulin resistance, heightened risk of diabetes, cardiovascular disease and so on. The two are linked, but not the same problem.

i’m confused why you considered this healthy?

> 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.

> Glycemic spikes on the other hand are linked to increased insulin resistance, heightened risk of diabetes, cardiovascular disease and so on.

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.

Dried mangoes don't have fibre? How does drying them remove it?

I thought the same, seems obvious to me but I think a lot of people are still following the food pyramid and "all fat is bad" propaganda.

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.

They do have fibre, but a large part of (non-dried) mangos are water. If you remove the water, then the sugar density per volume/weight goes up a lot.

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.

There's a popular subculture moment happening where non-diabetic folks are tracking their glucose since it's now possible to do without great expense. Similar to recent trends with step counters, heart rate monitors, etc. The necessity of tracking for diabetics has led to the opportunity for others.

White bread has a bad carbohydrates per protein ratio, but nonetheless it has a much higher protein content than almost any other cereal (i.e. except oats) and a much higher protein content than anything else with a comparable price.

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.

thank you for catching that, i misspoke regarding the fiber. My bad.

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.

Why is butter an unhealthy fat?

i’m not a licensed nutritionist so i’ll defer to the experts. My recall on the details is not the best, simply what i remember from a few nutritionist sessions my wife had. :)

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.

Butter is primarily saturated fat, it’s often considered unhealthy due to its potential to raise LDL cholesterol and increase the risk of heart disease. Nothing wrong with butter - in moderation. And it’s great to get healthy fats into your diet!

Healthy fats are monounsaturated and polyunsaturated fats (“unsaturated”). Found in things like nuts, olive oil, avocado oil, fish, etc.

By "cereal" I have meant cereal plants, i.e. wheat, rye, barley, oats, rice, maize, millet, sorghum and so on, in their raw ingredient forms, i.e. as grains, meal or flour form.

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.)

oh i see. I’d probably refer to that category as simply “grains” or “cereal grains”.

I’m in agreement!

As another poster has said, due to it high content of saturated fat. Butter remains healthier than butter substitutes, e.g. margarine.

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.)

The risks related to glycemic spikes are a widely accepted fact in the medical community, it's not even remotely close to being a controversial opinion. See [0], [1] and [2] for a start, but really, there's a very wide body of research on this matter along with ample evidence.

[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...

> much like the previous "common sense" wave of "fat makes you fat" that led several generations into a dead end.

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 :-)

Makes sense. Perhaps you were thinking of juice.

highly interesting!

Very high in AGEs

No, not really. There's an established correlation between glycemic spikes and health risks which the papers you reference confirm. But correlation is not causation, and I haven't seen any evidence that reducing spikes have positive long-term consequences for general population (not diabetics). Would be interesting to see a controlled test if it ever happened.

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.

> 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

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.

The key problems of glycemic spikes:

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.

You’re suggesting a french nutritionist would _encourage_ eating a baguette with butter as a healthy meal? That’s surprising to me. I suppose it _can_ be OK for a person who’s in good health already, but i wouldn’t purposely choose it and feel healthy about it lol. I can think of many alternatives that actually offer nutrition too. Like a banana, or baguette with a small side of sautéed peppers or mushrooms.

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!

> Corn syrup has way more calories por unit sweetness.

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".

I'm aware of this theory and it sounds very logical, but essentially it's hand-waving that is not backed by controlled trials or observational data [1][2] What's described above is not necessarily a "problem", it's normal functioning of human body.

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...

> i’m confused why you considered this healthy?

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).

But your first point already admits an energy surplus while this thread is talking about a negative effect supposedly modulated by a glucose/insulin spike in isolation.

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.

> Obesity is concerned with calories in and calories out

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.

Exactly. Dried fruits (and dried mangos in particular) may seem healthy, but you should treat them like candy. In fact it's worse than candy - at least chocolate has fat, which makes you feel full, while dried mango is pure sugars and carbs.

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.

The type of bread matters. Fiber dampens the spike.

GP asked for causal rather than correlational links for non-diabetics, which I provided.

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.

If you wear a glucose monitor and experiment a little, you'll find that the composition and timing of meals matter a lot. Eat high glycemic index stuff on its own: big spike, big crash. Eat it with slowly digesting stuff: hardly a spike. It makes sense if you mentally trace how the food you ate will be moving through your digestive system.

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).

Glycemic spikes makes me hungry after the spike. This indirectly caused my obesity, among other factors of course. It was a loop of eat something that spiked my glucose, be super hungry 40 minutes later on the drop, spike it again. Repeat.

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.

> My weight is stable but each time I go to US for a couple of weeks I bring back 3-5 extra kilos

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.

> Or perhaps steel cut oats, with thin sliced banana.

Can anyone explain how the thickness of the banana slices affects the healthiness of the meal for me?

Glucose awareness is an ever-moving target. It's why it can be dangerous for anyone with diabetes.

kudos to you for taking a proactive interest in your health. I feel the same way about education in schools. The nutritional education I did receive in school was really poor.

it doesn’t, just makes for fancy presentation. I usually layer thin slices of banana on top of half of the bowl.

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.

Lmao, I love the honesty combined with me trying to find deeper meaning where there was none.

It's delicious BTW.