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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.

> 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.

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...

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.

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.

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...

The type of bread matters. Fiber dampens the spike.

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).

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.

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.

> 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.

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.

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.

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.

> 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 :-)

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

> 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".