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Continuous Glucose Monitoring

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116 points zdw | 6 comments | 30 Jun 25 02:09 UTC | HN request time: 0.001s | source | bottom
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guiambros ◴[30 Jun 25 04:33 UTC] No.44419406[source]▶
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...

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alexey-salmin ◴[30 Jun 25 05:43 UTC] No.44419818[source]▶
> 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.

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Etheryte ◴[30 Jun 25 06:45 UTC] No.44420201[source]▶
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.
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alexey-salmin ◴[30 Jun 25 07:44 UTC] No.44420546[source]▶
> 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.

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Etheryte ◴[30 Jun 25 10:31 UTC] No.44421577{3}[source]▶
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...

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alexey-salmin ◴[30 Jun 25 17:31 UTC] No.44425870{4}[source]▶
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.

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1. dinfinity ◴[30 Jun 25 18:30 UTC] No.44426395{5}[source]▶
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.

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2. alexey-salmin ◴[30 Jun 25 20:20 UTC] No.44427403[source]▶
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...

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3. hombre_fatal ◴[01 Jul 25 01:09 UTC] No.44429589[source]▶
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.

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4. dataangel ◴[01 Jul 25 04:18 UTC] No.44430555[source]▶
The type of bread matters. Fiber dampens the spike.
5. dinfinity ◴[01 Jul 25 04:37 UTC] No.44430625[source]▶
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.

6. dinfinity ◴[01 Jul 25 04:52 UTC] No.44430691[source]▶
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).