AMA #24: Deep dive into blood glucose: why it matters, important metrics to track, and superior insights from a CGM

**Peter Attia** (0:11)
Hey, everyone, welcome to a sneak peek, Ask Me Anything, or AMA episode of the Drive podcast. I'm your host, Peter Attia. At the end of this short episode, I'll explain how you can access the AMA episodes in full, along with a ton of other membership benefits we've created. Or you can learn more now by going to peterattiamd.com forward slash subscribe. So without further delay, here's today's sneak peek of the Ask Me Anything episode.
Hey everyone, welcome to AMA number 24
In this episode, I am joined as usual by Bob Kaplan, and we devote the entire episode to a series of questions that focus around glucose homeostasis. We centered the discussion basically around the idea of why one would wear a CGM, especially someone who does not have type two diabetes or type one diabetes. And we get into the really deep nitty gritty around what is it about glucose that matters so much with respect to health? Why is it that I make such a stink about having lower average blood glucose, fewer peaks of glucose, less glucose variability, and all of the associated things that go with it? So hope you'll check out AMA number 24 And without further delay, here it is.

**Bob Kaplan** (1:31)
Hello, Peter.

**Peter Attia** (1:32)
Hey, Bob.

**Bob Kaplan** (1:33)
How's it going?

**Peter Attia** (1:34)
It's going well, man.

**Bob Kaplan** (1:36)
Ready for an AMA?

**Peter Attia** (1:38)
Ready as always.

**Bob Kaplan** (1:39)
All right. So in this case, we got great questions about glucose, and we aggregated a bunch. I think it would be good to do a deep dive. I'm going to go through a couple of questions here, see what you think.
So the first question is more of a statement than a question. I've heard Peter talk about how fasting glucose and even HbA1c measurements can often be misleading, and how he favors OGTT, which is short for Original Gangster Time Trial.

**Peter Attia** (2:11)
That's right. Yeah.

**Bob Kaplan** (2:12)
Perfect. I think it might be oral glucose tolerance test with insulin measurements, and also wearing a CGM to get a better sense of glucose homeostasis. My understanding is that OGTTs and CGMs are typically reserved for people with diabetes.
So he's got the following questions. Why does Peter find these tests useful in quote unquote healthy people? What is Peter looking for when assessing someone's glucose levels? What does he like and hate to see? How does Peter define normal versus abnormal control of glucose?
If I'm not diabetic, do I have anything to worry about here? And there's another question that was, are you able to do a breakdown of what you look for on different people's CGM data and what you would advise to improve their numbers? Similar to the AMA you did on lab tests.

**Peter Attia** (3:00)
All right, so I'm going to pause you right there, Bob, and I want you to answer this question for me honestly. Did you pay this person to ask these questions?

**Bob Kaplan** (3:10)
Asking for a friend.

**Peter Attia** (3:12)
I mean, seriously, these are the perfect questions, the most salient questions, the most important questions.
And this might become by extension then one of the most important AMAs we do in terms of the aggregate impact it could have on health and longevity. Because these questions really get at the root of where I think, I hate to use this term, but for lack of a better word, where the mainstream medical system is just so out of sync with what I believe the future of medicine is going to be. So let's take a step back on all of this for a second.
Type 2 diabetes has a definition, and it is defined as having a hemoglobin A1C concentration greater than 6.5%. And that corresponds to an average blood glucose, God, I should know this, but the fact that I pay so little attention to it tells you why I don't even know it. I believe it corresponds to an average blood glucose of approximately 130 milligrams per deciliter. And of course the way it works is it measures the concentration of glycosylated hemoglobin. So it's taking out red blood cells and it's looking at how much glucose is stuck to them. And obviously the more glucose that is stuck to them, the more you can infer that the average concentration of glucose is higher during the period of a red blood cell's life. But of course this is potentially misleading because if a red blood cell has a very short life, for example, see this in a couple of my patients, including a patient who's recovering from prostate cancer who still has some GI bleeding issues, patients with gastritis, et cetera, women with a heavy menstrual period. So people who are losing significant amounts of blood have a higher turnover red blood cells. They're going to have an artificially low hemoglobin A1c. Conversely, people who have red blood cells that stick around a very long time, people with a microcytic pattern, meaning they have very small red blood cells that are less likely to get chewed up in the splenic system, which is where we ultimately break down red blood cells, they're going to have an artificially elevated hemoglobin A1c because their red blood cells are living longer on average than the typical person, which is about 90 days. So that's one reason why I'm not a huge fan of hemoglobin A1c. But the broader point here is that I find it unhelpful to simply say if your hemoglobin A1c is above 6.5 and you have type 2 diabetes, you have quote unquote a disease. If it is below 6.5, you are normal. Or even if we go one step further and say, well, there's a pre-diabetes, which is defined as 5.7 to 6.4, and those people we have to watch out for, but anybody at 5.6 and down is completely normal. As though there's some enormous difference between 5.6 and 5.7, or 6.4 and 6.5. So while on the one hand I understand the need to simplify things, I think oversimplification is erroneous, and I think we should view these as a continuum. So glucose at the average level is a continuum.