Assumption: Medical professionals are trained to use Evidence Based Medicine (EBM).
One might assume that EBM means something specific, and I'm sure it does, but that specific thing is different for different people.
One thing that EBM sometimes means is: common sense is no substitute for evidence. There are uncountable times that common sense has been wrong in the medical context.
So, you have a lot of people commenting here that this is obvious common sense, but many medical professionals will pull out a reference chart of caloric content and glycemic index and say "look at the evidence".
So, it is very useful to do studies that bring evidence to common sense.
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My other pet peeve with EBM is that it does a poor job of understanding that different interventions work for different people - it is time consuming and expensive to do that kind of investigation, thus some/many medical professionals do not understand or believe it.
This comment is intended as a critique, not a dismissal.
At the top of the evidence hierarchy is N-of-1 trials (and below that are high quality meta-analyses of trials). Nothing is more informative about treatment response in a person than testing it in that person. This is the heart of personalized medicine, and exactly for the reason you stated: Different interventions work differently for different people.
And any practitioner worth their salt is unsurprised by this headline. A great example is that illness and inflammation increase insulin resistance via counter-regulatory hormones.
You got one thing right, intuition often turns out to be wrong. That is why the vast majority experimental therapeutics built on great ideas never get passed initial testing.
Such tools also enable studies that can be done at a scale and cost level that is reasonable and can push forward the communal knowledge base.
1. You wear a CGM for 2 weeks, and log everything you eat.
2. At the end, you get a personalized report about how different foods that you ate affect you, personally. And they can extrapolate to other foods that you didn't eat during the testing period.
3. Zoe's model gets better and better the more people sign up, and the more data they get.
Either way, if something as simple as eating a few bites of bacon before you eat your toast can change your glucose response, manually logging your meals for Zoe isn’t gonna provide enough data for any reliable extrapolations.
I'm not sure - the fact that it does vary from person to person, doesn't mean there aren't groups of people for whom it behaves more predictably, which could be clinically useful.
I would need to see an independent researcher confirm they can do this. As of now, I don't believe they can, and I'm not even sure the theory is reasonable.
And how do you know that the logs are accurate? The best subjects are incarcerated subjects.
All that said, it's a long row to hoe, and the monitors are definitely worth all the annoyances; they are way better than peeing on a strip of testape like we did back in the old two-holer. But science is very hard.
There's a lot of reductionist commentary that happens under these links primarily because people aren't reading past the headline or a brief skim of the article.
The topic might be common sense, but measuring and quantifying it with hard data is valuable.
The PR-massaged headlines usually omit the interesting parts and focus on something basic because they want to appeal to a wide audience, not because the study itself was so simplistic that it could be summarized by a headline.
This has not been my experience with doctors throughout the years. In fact, I'd say the opposite has been true.
In my experience, particularly when diagnoses are trickier, doctors are more likely check the efficacy of the current treatment and change things up if it's not working out.
You have this about everything, everywhere. It's a pet peeve how much stuff people will attribute to "common sense" so they can do the internet "I'm superior" thing.
"Wear sunscreen, it's just common sense". No it isn't. We evolved on Earth under the sun, we feel good when going out in the sun, it's bright and beautiful. Rubbing petrochemical distillate or industrially processed plant extract on your skin so the invisible light discovered in 1801 doesn't denature the invisible DNA discovered in 1869 is not common sense it's learned behaviour. Nothing much about Science is common sense, it took thousands of years from the dawn of Civilization until the Enlightenment era and still people can go through years of education and then choose to believe what we want to believe instead of what the evidence shows.
'Common Sense' is that the world is simple, designed for a purpose by a human-like mind one or two levels up from us on the power scale, and inhabited by life-like energies and spirits, some of them malevolent. Common Sense is that things which didn't happen today or yesterday will probably never happen. Common Sense is that things which happen together cause each other; if the relative comes to town and the crop fails then they are bad luck, if the relative comes to town and the baby is born healthy then they are good luck.
Why would it be any kind of 'common sense' - 'sound judgement not based on any specialised knowledge' - that glucose (1747) response differs for the same meal if you need a continuous glucose monitor (FDA approved in 1999) to find that out?!
knowledge, judgement, and taste which is more or less universal and which is held more or less without reflection or argument. As such, it is often considered to represent the basic level of sound practical judgement or knowledge of basic facts that any adult human being ought to possess.
And this isn’t even universally true. It’s tied to skin color. Sunscreen won’t do much for someone with extremely dark skin. In medical lit, “common” often refers to “white persons.”
Literally all medical practitioners are trained to take individual people circumstances into account.
The problem with studying humans is, roughly, the central limit theorem doesnt work: properties of biological and social systems do not have well-behaved statistics. So all this t-test pseudoscience can be a great misdirection, and common sense more reliable.
In the case where effect sizes are small and the data generating process "chaotic", assumptions of the opposite can be more dangerous than giving up on science and adopting "circumstantial humility". (Consider eg., that common sense is very weakly correlated across its practicioners, but "science" forces often pathological correlations on how people are treated -- which can signficantly mangify the harm).
Citation needed?
I don't know what would lead to that conclusion. And it would seem to run counter to the entire history of the field of psychology, for example.
Psychology is the field that is most hit with replication failures and has a slew of unintuitive results that turn out to be malpractice.
So that's why I question the assertion. You're right that there are tons of replication failures, but whether intuition correlates with replicability way doesn't seem relevant. Especially when the point of so much research is to look for currently "non-intuitive" things, so of course that's where more replication issues might exist. It doesn't mean you should stop researching in that direction.
Decreased sleep slow-wave activity (not just sleep time, but the actual restorative function of sleep) significantly decreases next day insulin response [1].
This is my area (I work in neurotech/sleeptech), but other things that come to mind are changes in changes in gut biome, which can be altered by previous meals, and I assume is always in flux (not my area of expertise), hormonal changes, I'm sure there are others.
However, the conclusion that it undermines the CGM measurements. In fact, I think this makes CGMs more valuable, not less. For those without diabetes, I always thought you'd use the CGM for a few weeks, figure out what your body responds to, and then sort out your diet.
This shows that it isn't that simple, and that we likely need to be monitoring more regularly. If my breakfast spiked my glucose unexpectedly, that may be a signal that I should change my lunch in order to reduce the likelihood of another spike. It becomes about constant management, rather than a 1 time look under the hood.
This was my plan sometime in the next few months.
I think it's still a valid plan, just with some caveats. Anyway due to cost and annoyance I'm unlikely to wear a CGM for more than a couple of months. But that should be enough time to get usable data - like all body tracking data, I'll end up using it as guidance rather than rule.
The caveats are that I'll also need to track my sleep and workouts during that time and carefully look for patterns in the data related to all three.
I already know sleep and workouts are strongly correlated and not always in the way you'd expect. I did a strong HIIT class at 6pm last night, and due to a bit of crunch on personal projects it was my first proper workout in a week. My sleep tracker (Galaxy Watch 6) gave me a very poor sleep and energy score. 61/100 for sleep, 69/100 for energy. I normally score high eighties to low 90s in both.
These scores usually but not always match with my actual feeling. But today I also feel tired (it's 8am here now).
If I had a CGM, I'd also be keeping a strong eye out for unusual glucose response today.
This is more complex than I'd like it to be - I wish my body was as simple to read as just getting a single number like glucose response and making adjustments from that! But as a lifelong migraine sufferer who now has my migraines almost entirely under control by making lifestyle changes, I'm well aware that how my body responds is always a combination of many things. Stormy weather + ate cheese + slightly too strong coffee + stress from work = boom, migraine. Take away any one of those and maybe I wouldn't have got one. I fully expect my body's glucose response to be just as complex.
A carb-heavy snack before a meal is going to result in a radically different response than eating the same meal on an empty stomach. I'm glad they acknowledged it, but it feels absurd to publish with this headline if they didn't record snacks.
Asking for a friend.
However, on a population level, it is known that shift workers have increased incidence of diabetes, heart disease, obesity, etc. Some of that likely comes down to socio-economic factors, but we can't ignore that daytime sleep or potentially even shifting schedules, is not as restorative as consistent sleep, regardless of sleep time.
I feel I haven't answered your question, but I think this is the best I've got.
why don't they test it. should be easy create a study?
As the authors mention in the end, personalized nutrition based on CGM only makes less sense than also integrating sleep, stress, movement,... - which Oura is really good at.
Another thing I've noticed is that if I eat a very rice-heavy meal, my blood sugar levels may rise throughout the night. I don't think this is insulin-resistance but rather my body digesting the rice. You can't expect the body to digest all the rice in 2 hours, can you, there certainly must be parts that are protected from the stomach acid until much later in the digestion process. So that feeds into the high blood sugar levels overnight in my opinion.
I think if anything, CGMs have opened up the idea of what diabetes really is and how different bodies handle blood sugar. I think I'm borderline T2D, not full-on T2D despite what my doctor says, and I've started wondering if my blood sugar has always been high, but normal for me. On average it's about 120 mg/dL, but I do see my body react properly to new sources of blood sugar and drive it back to "normal" levels, so the idea that I have insulin resistance doesn't make sense to me.
For convenience and my experiment, I eat practically the same meals at lunch every day, precisely weighed, always starting from very similar morning glucose levels, and strictly respecting timing and consistency.
I NEVER get the same response. Never. It’s an experiment I’ve been running on myself for a year. It’s useful for me, but for the diabetes team following me, “that’s not possible, there must be other factors, it doesn’t show, it’s the ‘CGM algorithm’” (a mystical object no one knows anything about, except that it’s supposedly intelligent).
This study is interesting. I hope this kind of information, this doubt, trickles down into the medical community. Even though I don’t have much hope. Maybe in years and years.
Note: This is pure speculation, and I'm not claiming to know anything more than passing knowledge about diabetes.
Sometimes my blood glucose will be high-ish like maybe 135. Then if I drink some coke, ie pure sugar, it causes my blood glucose to spike and then my insulin kicks in and it drives it back down to 110-120. It’s as if the switch to turn on the insulin wasn’t turned on because there was a slow steady creep up of blood glucose and then it needed to be woken up.
The body sure is strange but one thing I do know is that CGMs are changing things for sure.
(Purchased sorta 'just for fun', to evaluate my own metabolic responsiveness. I wrote about it once: [0])
if I moved around much after eating, my muscles would "soak" lots of glucose from my blood and the insulin change would be relatively low. If it was something sugary and I then went to sleep, it would be a big slow rise for a few hours of blood sugar, then insulin would seem to be released, and it would decline a bit, then flatten, then decline, until it went back to a regular level. When waking up, it would often by around 70 mg/DL, and even if I eat zero carbs (or am full-on fasting!) it would bounce up/around during the day. I appreciated that my body seemed quite capable of doing whatever it needed to do to raise my blood glucose levels. (They always go up when exercising, for instance, even if no food is consumed)
I think everyone would likely find the data interesting, it's so freaky customized to yourself, it cannot help but be interesting. They're expensive, so I think buying even one sensor and wearing it for 2 weeks or however long is worth it.
Type 2 "resistance" is about the quality of the response to high glucose levels, not the complete lack of a response to them. There shouldn't be a long buildup overnight in that scenario for a person without insulin resistance/deficiency and still having a measurable insulin response is normal/expected of all but the worst Type 2 diabetics. Yes, you're still digesting, but in individuals without diabetes the blood sugar peak occurs (and ends) well before digestion is finished because influxes of carbs can still be effectively managed by the insulin alone rather than by the lack of additional carbs to digest. If it were just that one's digestion were a lot slower than a normal persons then it should still result in a lower, but still quickly managed to baseline, peak.
You may well actually be prediabetic though, it just depends on the specific numbers for A1C/average & peaks combined over time and not the presence of a response itself. The recommendations between higher side prediabetic and lower side type II diabetic shouldn't be all that different in the end anyways though.
Just to clarify - A1C is itself an easily-measured proxy for diabetes mellitus, but it's itself a heuristic. There are groups for whom it is known that the "standard" A1C range is actually incorrect, because of confounding factors that affect the A1C measurement but are unrelated to the metabolic dysfunction or general sugar levels.
Your point is correct, though, that what OP is describing is consistent with diabetes, and the actual clinical recommendations for prediabetes and Type II diabetes are often the same, at least in the early stages.
I'm a type 1 and my blood glucose can response can vary wildly. Sometimes it can spike quickly (15-30 minutes), other times it can take 2, 3, or even 4 hours. The reverse is also true, in that insulin can sometimes effect me quickly, and sometimes it can take effect 3+ hours later. In general, when having a big meal, I'll take a "fairly large" amount of insulin, but not enough for the entire meal; then I'll take more[1] when my blood starts increasing into 200+ range. Otherwise, I risk it dropping because the insulin was having a "fast" day but the food was "slow".
My endo finds it weird, but we've gone over specific cases of it, including exactly what I ate, when, and what the CGM history for the day looked like. I'm just defective :)
[1] Note I'm not talking about reactively taking more insulin after the "right" amount turned out not to be enough (which is generally a bad idea). Rather, I'm talking about splitting what I know to be about the right amount... into 2 different doses.
Physical activity, mental activity, and sickness can also massively effect dose.
On days I'm physically active I feel like I need less than half the dose of insulin then days I'm caught behind a desk. This said, high impact mental stress that requires lots of thinking can rapidly drop my glucose level.
And that's not counting being ill where my body will pretend like it's insulin resistant for hours then suddenly try to process it all at once.
1. Temperature (room / outside)
2. How well you’re hydrated
Regarding the *time* it takes for eaten Carbs/glucose to enter the bloodstream, it seems that simply standing/being postural often slows down digestion, while sitting/laying down (think of a couch potato watching tv) seems to increase digestion speed.
Typically the glucose level in the interstitial fluid takes longer to respond to your food intake, and the GCMs measure that instead of the blood glucose level.
I think you could have a point at around 100-105 baseline but 120 seems too high.
I also found that sweets not only spiked my values but did so over a 6-12 hour period! That was shocking. I have not had dessert for 107 days because of it. I plan to do a fasting test (and A1C) in August to see how many values are. I hope they are much lower, but we'll see.
EDIT: also, popcorn with nothing on it but salt gave me a huge spike.
Neat to see what other people's priors are, on this.
I don't think anybody was expecting to be surprised by this study. In practice, most science is pretty boring and rarely breaks expectations. But being unsurprising does not mean it's not worth doing. A lot of studies are simply validating expected outcomes and providing foundational data points for future studies to refer back to. For example, a future study might use this study to justify funding ("as shown in Study 2025.abcd, glucose is highly variable... we propose to further study this by controlling for ... which will help us understand the influence of ..." etc etc).
I'll note that even basic physics has that problem. Try explaining to a 5th grader why a feather would fly in the same arc that a rock will take, if there was no air.
Well of course. Studies like this help collect data and quantify the variations.
There's more to the study than the headline or even the simple summary. Knowing the range of variations is important, as well as starting to build a foundation to understand some of the factors that lead to the variations.
Some of my learnings:
- Don't start your day with a large amount carbs. Have some insulin in your blood before eating that big bowl of oatmeal. Or just go for some yougurt with nuts and seeds.
- The classical order of a three course meal (salad first, then main dish, then dessert) is pretty good in terms of preventing glucose spikes.
- Going for a walk after a meal is great for bringing glucose levels down.
- Eat at least 2h before going to sleep. Having high glucose levels disrupts sleep.
- Alcohol lowers the glucose response of a meal, but is still bad unfortunately.
- Diet Coke works. No spike vs loads of sugar with a real coke.
- Stress can spike glucose like crazy, e.g. being in an interview or during takeoff.
- If you really want to know how you react to some food, keep the circumstances (time of day, sleep, physical activity, stress) similar. There's too much influence beyond just the meal.
I bet that everyone who is wearing a premium smartwatch or an Oura ring now will be using a CGM now and then in the next years.
[1]: https://pubmed.ncbi.nlm.nih.gov/32528151/ [2]: https://pubmed.ncbi.nlm.nih.gov/26590418/
I think it will/would take a lot of data to uncover the most important factor(s).
My wife is T1D and this is infuriating for her.
She’ll think that she’s cracked it, and then the next day, with the same meal at the same time, her sugar levels go high.
Her words: there is nothing else where you have studied for over 30 years and STILL feel like you know nothing.
It is incredibly demoralising for her sometimes - especially when she’s suffering also from a high/low sugar level. I have the upmost respect for anyone having to do the amount of work, to get to zero (sometimes).
For example, AAPS has since version 3.2 dynamic IFS. ( https://androidaps.readthedocs.io/en/latest/DailyLifeWithAap... )
For me this works quite well
- You able to learn better about how your body responds to different foods
- You are more secure about your blood sugar dropping when you don't expect/realize it (sleeping, driving, etc)
- You better able to detect when your body isn't behaving the way you would normally expect it to (the point we're discussing here)
I do keto diet long term but for other reasons, often the epilepsy version where it's more strict and higher fat.
there are plenty of good reasons we eat carbs (especially complex carbs, plus trying to avoid processed stuff); as a diabetic you just have to prepare ahead of time. it sucks, but honestly, as a 20+ year T1D, not eating cake sucks more than having to plan to eat cake :)
But you have never felt the alternative. It's not just eating cake. You have to see the whole video that I linked to understand the differences (they might not all apply). Think a smoker who've never known what's it like without smoking.
There are many levels to keto diet, and believe me, you can't do the epilepsy version even if you'd wanted, it takes time and hard effort, for children it's done inside a hospital.
So assuming you watch everything they eat, you can keep track of GCM, and try very slowly. Like going from 60-30-10 carb-protein-fat to 50-30-20 ratio, do they have better consistent blood sugar ?
There should be protocols to do this for T1D the safest way.
Watch the video.
> Other behavioral and individual factors are known to influence CGM responses.[22][6] Postmeal physical activity — even as minor as leg fidgeting[23] and walking for a few minutes every hour — reduces postmeal glucose responses.[24] Sleep quality has also been associated with changes in postmeal CGM glucose responses.[25] Emerging studies are also uncovering the relationship between an individual’s gut microbiome and their postmeal glycemic responses.[26][27][28]
So basically it's the impact of the parasympathetic/sympathetic nervous system and the order of food ingestion that could induce different glucose response.
It's interesting because I assumed that beside the nervous system, whatever order we eat our food, it all mixes in the stomach and then start to process. Negating the importance of order but studies implies it does.
The level of serotonin and its interplay with our current level of immune response/inflammation in our body is the single best predictor of insulin resistance. That’s simply because every good thing you can do to lower resistance increases serotonin. Serotonin then decreases inflammation. When you exercise for a long period of time you are not only increasing your immediate availability of serotonin, you are also increasing your daily availability for serotonin.
Obviously it’s a little more complicated but from a big picture standpoint, either something is increasing inflammation in you today and increasing your insulin resistance or (hopefully) the opposite is happening and serotonin is moving your insulin through your blood stream like a mag lev train.
On a side note, I do love cgms.
My graph: https://i.imgur.com/FzPdH1g.png
Mom's graph: https://i.imgur.com/5DR1G30.png
Discussion: https://reddit.com/r/PeterAttia/comments/1k301o4/my_ogtt_exp...
The symptoms of excitement are of course similar to the fight-or-flight response. Raised heart rate for one. Butterflies in the stomach indicate release of adrenaline, which in turn raises blood glucose -- not from the food being eaten but from the body's stores. So there's a link right there.
How excited you are about a given food will depend not only upon the foodstuff itself but also on your personal taste and personal history. If you have taken pleasure in its consumption many times in the past this may affect your present level of excitement.
'Arousal' is another word that just sprang to mind.
``` This page summarizes a study about continuous glucose monitors (CGMs) and how individuals can have highly variable glucose responses even when eating the same meals. The study, which involved 30 participants without diabetes, found a weak-to-moderate correlation between glucose responses to identical meals, with about 80% of the variation attributed to within-participant differences or measurement error.
The article notes that high glucose variability is linked to increased risk of death, greater hunger, and poorer mental health and sleep. While CGMs are beneficial for people with diabetes to prevent hypoglycemic episodes, this study suggests that developing personalized nutrition recommendations for glycemic control may be more complex than previously thought due to inconsistent individual responses. The authors emphasize the need for more reliable dietary assessment and a deeper understanding of the behavioral, dietary, and individual factors that influence glucose responses. ```
