The REAL Reason Your Brain Loves Ketones

Added: 2026-06-10

[00:00:00]Okay, I want to zoom back now and talk about different substrates used to make energy. We've been primarily focused on the ketone.

[00:00:06]We also have glucose, which most people are relying heavily on.

[00:00:11]But there's also fatty acids.

[00:00:15]And then there's also the nuance of the blood-brain barrier and fat as a medium for making energy, there's a limitation there.

[00:00:25]So basically I want to talk about how the body decides when to use fat versus make ketones in the liver endogenously. And then I want to bring in the brain aspect and how the fatty acids don't cross over readily.

[00:00:40]>> Sure. So when someone's regulating between just fat production in general, it's regulated by insulin. So insulin load is really going to predominantly regulate how much fat is being broken down or oxidized as the primary determinant. Okay, and the fast way best way to determine insulin levels is usually through dietary components and the the one that rises insulin the highest is carbohydrates. Reduces it the lowest is when you go to a lower carbohydrate approach. Beyond dietary components, which are the most potent, there is body weight. Excess adipose tissue reduces insulin sensitivity and you produce more insulin to try to produce the same effect and as a result, typically you are less capable of actually getting to fat oxidation state.

[00:01:19]So a characteristic of type 2 diabetes is a a high glycolytic or glucose dominance as a form of energy or metabolism.

[00:01:28]And less fat oxidation. So again, it's really regulated predominantly in the in lifestyle through insulin levels.

[00:01:35]Beyond insulin levels though as a way to regulate how much fat the body is burning, typically ketone bodies come along in a dose-dependent manner with higher levels of fat oxidation. So as fat starts to rise as a as a byproduct of of fat breakdown, they typically go hand in hand. So at that highest levels of fat oxidation are typically when you have the highest levels of ketone production.

[00:01:59]Now, I had mentioned lifestyle factors like nutrition and then also body weight as a way of dictating insulin sensitivity versus resistance. We also know exercise is a powerful way to increase fat breakdown as well as ketone production as well. So, uh those are the kind of key determinants of how something or how the body it through lifestyle interact together to regulate fat oxidation and also ketone utilization. Now, you asked a question about the brain and fat getting to the brain. Well, we know that some fats can get into the brain like medium-chain triglycerides. But, if you consume medium-chain triglycerides, your body tends to convert them in the liver before they even get to the brain.

[00:02:38]Long-chain fatty acids are the type of fat that you store on your body.

[00:02:42]They're also the form that are most predominant in the diet. So, when you're consuming olive oils or other forms of oils, typically uh when you think of fat, they're typically long-chain.

[00:02:52]Now, those fats don't readily cross the blood-brain barrier and uh provide the brain with energetic substrate. So, as a result, when you're consuming a lower carbohydrate-based diet and you consume less glucose, but fat doesn't cross the blood-brain barrier, there is concern. Oh, no, the brain's going to become glycopenic, meaning glucose uh reduction in glucose lower than the brain needs to sustain its optimal energetic needs, and you're going to have a brain energy deficit, and you're going to get into something called hypoglycemia, which causes neurological deficits and cognitive decline, reliably.

[00:03:28]So, how does your body make up for that?

[00:03:29]Well, it's built this beautiful machinery within the liver where it converts this excess fat over to ketone bodies to then make up the energetic needs in the brain when glucose is reduced. This is the primary way in which ketones are actually neces- necessary in the body, okay? They obviously have almost hormonal-like components, signaling components, and metabolic components, but they also play the most fundamental role in survival when you're in a faster or famine evolutionarily speaking by ensuring the brain doesn't go into an energetic deficit when you're deprived of the ability to consume food, so deprived of energy.

[00:04:07]And that's because the fat can't just go to the brain and and make up for glucose as a fuel. It had to convert it to something that crosses the blood-brain barrier and can be readily metabolized by brain brain tissues. And those are ketone bodies. So, that's how the body works to regulate that. Um but another example of that is lactate. So, the body when it goes to extreme forms of exercise, let's say you're evolutionarily speaking having to run miles and miles and miles, maybe even uh you know, 20 plus miles to get your fuel and you're producing more lactate, well, the body knows that all of a sudden you're producing more lactate, it's going to now utilize that as well as an energy source. So, it's producing more lactate, more ketone bodies for these prolonged forms of exercise.

[00:04:47]What your body is really trying to do here, Jesse, is trying to ensure the brain is always energetically sufficient. So, when ketones and lactate are present, typically evolutionarily speaking, they are only going to be present, at least ketone bodies, in an energetic deficit environment. Now, we know we can follow a ketogenic diet or apply exogenous ketone bodies, but evolutionarily speaking, typically it was an energetic deficit.

[00:05:08]Lactate is produced through high levels of exercise over prolonged periods of time. Um but when both of those are present, Jesse, they're actually consumed by the brain in a dose-dependent manner.

[00:05:18]Glucose is only consumed in the brain proportional to the brain energetic needs.

[00:05:23]Why is that important?

[00:05:25]It tells us how the brain or the body self-regulates.

[00:05:29]It is saying that the body says, "Okay, if I have ketones and lactates present, I need to utilize those first because I might be in a crisis uh for brain energy glucose deficits. So, I need to spare glucose and make sure that I'm utilizing these other substrates the bodies have limitless supplies of in the theory of ketones because of fat breakdown or lactate uh because of conversion of glucose over during exercise. So, that's how the body is telling us what it prefers. If you give glucose or ketones, the body will preferentially utilize those over glucose in a dose-dependent manner.

[00:06:04]And that tells us the body's when those substrates are available or going to prioritize those over glucose. And we see that in MRI scans when you co-administer glucose and ketones in the brain and see that ketones are readily utilized in a dose-dependent manner and glucose is not.

[00:06:19]So, these this is all explained through evolutionary lens of self-survival.

[00:06:24]>> As you're sharing all that, it gets me thinking about somebody trying out this diet and maybe missing the mark on getting the carbs low enough to produce ketones.

[00:06:34]So, they're not bringing in a lot of glucose.

[00:06:37]They might just be bringing in enough glucose through carbs or sugar to block the fatty acids from being released and used as energy. Then we also have the blood-brain barrier piece.

[00:06:51]What I'm getting at with all this, if you're not lowering the carbs, getting the ketones, you're not really getting the glucose through the diet that you were before, I could see how specifically in the brain and the rest of the body, you could have a real energy problem.

[00:07:06]>> Correct, which is why the body has this machinery in place, which is also why we see that when you exogenously administer things like ketone bodies, there seems to be metabolic benefits to them, at least acutely speaking, as the body tries to utilize those preferentially.

[00:07:20]So, there's ways in which we understand how biology is working even from a self-survival mechanism that has elucidated opportunities to optimize the already well person by leveraging these same tools on top of normal standard dietary environments.

[00:07:33]>> Okay, just to make sure you're clear on what I was getting at there cuz I was kind of butchering it a bit.

[00:07:38]We're not taking in a lot of carbs or sugar, but we're taking in enough that we're not producing ketones. So, we're kind of at this energy-depleted state.

[00:07:49]I could see how a person could suffer in that thinking, "Oh, I'm just working my way into ketosis." If they're new to this, having a bit too many carbs, and they're not getting to the promised land of producing ketones and feeling good.

[00:08:02]>> Well, this is actually a very important point because most of the benefits that we see from carbohydrate restriction are at the ketogenic threshold. When insulin is sufficiently low to start producing ketone bodies at meaningful levels, again, 0.3 or higher, most people define as 0.5 or higher, but I typically say 0.3 or higher. And this is the threshold in which we see most of the clinical and metabolic benefits associated with this diet.

[00:08:24]But, there's also, to be fair, evidence that shows that if you just reduce carbohydrates in general down to less than 130 g per day, somewhere between 51 and 131 g, or sorry, 130 g, that this also has uh potential therapeutic benefits as well in regulating diseases like diabetes uh and obesity, where it can assist in in helping improve glycemic control. But, keep in mind, it's typically shifting, Jesse, from a standard American or Western diet over to a lower carbohydrate diet. So, by default, they're making a shift in a positive direction. But, you're right. I mean, you bring up an important point where someone's not actually kind of crossing that threshold, they may not be maximizing or reaching the the full potential of these interventions.

[00:09:06]>> Since you made it to the end of this clip, I know you're going to love the full episode. Click here to watch. I'll see you over there.

[00:09:12]>> A very low carbohydrate and very high-fat diet known as the ketogenic diet has been known to have powerful [music] metabolic changes. When people utilize these high-carbohydrate diets since the 1970s as the one optimal form of diet, it is for