Last Thursday, the day before the operation, the dental surgeon told me: "Make sure you have a good breakfast. I don't want you to get hypoglycaemic. It will last several hours." I replied: "I never have breakfast, and it is impossible for me to become hypoglycaemic." He was like: "What? What are you talking about? I don't understand what you're saying." I just said: "Because I don't eat carbohydrates, I cannot become hypoglycaemic." I'm not sure he understood what I meant, but I suppose that given my response, he figured I knew what I was talking about.I'm sure you've heard, at one point or another in your life, someone say: "I'm hypoglycaemic, I need to have something", and then seen them pull out a can or bottle of juice, an apple or an orange, a granola or a chocolate bar? Maybe you've said it yourself! It sounds scientific; like we know what we're talking about. Don't you think? Maybe we've heard a doctor or a nurse say it. Maybe we've heard other people say it, here and there. And over time, saying this has become common parlance in North America, and surely in the UK as well. But what does it mean? What do we mean when we say that?Do you know why I said what I did to the dentist? Do you understand why it is impossible for me, (and possibly you too), to become hypoglycaemic, even without eating for 12, 24, or 36 hours? Why is it that so many people suffer from hypoglycaemia on a daily basis, especially type II diabetics, and all the while, I'm writing that it is 'a metabolic impossibility'? Am I wrong? Am I lying? Am I confused or trying to be confusing? And why is there so much hype about hypoglycaemia? Just Google it and you'll see: 6.35 million hits! There's even a Hypoglycaemic Health Association!First of all, if you don't already know what it means, hypo means low, and glycaemia means 'sugar in the blood'. So, hypoglycaemia just means low blood sugar. But the thing is that what people usually mean when they say this, is that they are feeling tired, slow, flat, low-energy, light headed, maybe even dizzy, and interpret these symptoms to reflect a state of low blood sugar, which it usually does. But there's a caveat: different people will feel the same symptoms at different blood sugar levels! Isn't that a little weird? Doesn't that make you wonder about what this means and implies? If there is such as thing as hypoglycaemia, why would it be different for different people? Meaning, why would a certain blood sugar level be fine for one person, and too low for another?But what is low blood sugar? What is high blood sugar? What is normal blood sugar? Do you have any idea? And how much sugar is that, actually, circulating in the bloodstream? Any idea about that?Let's make it simple. Most people have between 5 and 6 litre of blood. Let's take 5 litres as our baseline to make the numbers easier. Most people, on average, have around 100 mg/dl of glucose in their blood (even if they should have less!) Since there are 10 dl in 1 litre, and 100 mg =0.1 g, this makes 5*10*0.1 g = 5 g. Think on that for a second: in your entire body, there are 5 litres of blood, and in this volume of blood, there are 5 measly little grams of glucose. That's a teaspoon!For very low blood sugar levels, we can go down to about 50 mg/dl (half the normal average). This would amount to just 2.5 g in your whole body! And for critically (as in dangerously) high levels, we can go up to around 400 mg/dl (four times the average). In this case, that would amount to still just 20 g! Therefore, we can say that at any given time in our body there is on average 5 g of sugar, very rarely less than 2.5 g, and only extremely rarely, when we are severely diabetic, up to 20 g. So, all things considered, it's not much, is it?Now, why is it that most people feel hypoglycaemic at one point or another if they don't eat for a while, sometimes in as little as a few hours? Why would different people feel these symptoms more or less intensely? And why would different people feel the same unpleasant or even debilitating symptoms of hypoglycaemia at different concentrations of blood glucose?Well, if you feel symptoms of hypoglycaemia it means that 1) your blood glucose levels are significantly lower than your own usual average level, the level at which your system and cells have gotten used to functioning. This average level could be 200, 150, 120, 100 mg/dl or whatever. And the lower threshold before you start feeling weak, tired or even dizzy could be 40, 50, 60, or even 90 mg/dl. In fact, diabetics or soon-to-be-diabetics, could be walking around, going about their business with an average of 150, 200 or even 300 mg/dl without knowing it, until they get a blood test and someone notices. And they would definitely feel hypoglycaemic at levels that could be quite high. How come?The key to understanding this conundrum in the apparent subjectivity of hypoglycaemia is the notion of glucose tolerance. But what is glucose tolerance if it is not insulin sensitivity? And what is insulin sensitivity if it is not the flip side of insulin resistance? I hope that by now, having been reading this blog for a while, you know everything about insulin resistance, how it develops and how it manifests itself in the biochemistry and metabolic functions of the body. (If you don't, then just reread the posts you'll find in the Diabetes and Carbs categories.)This notion of tolerance explains it all very neatly: with chronic exposure to glucose, (as in high average levels of glucose in the blood for an extended time), insulin resistance increases, and thus, insulin sensitivity decreases. As insulin sensitivity decreases, more insulin is needed to clear the glucose from the bloodstream, and more glucose stays in circulation longer. The cells get used to this high level of insulin, and become less and less sensitive to it, allowing less and less glucose to get in. When the level of glucose drops below the threshold at which the cells can use it without much effort, muscle but especially brain cells, we feel hypoglycaemic. This is why hypoglycaemia is defined on a subjective and relative scale that depends on our own cells' sensitivity to insulin, the hormone that shuttles the glucose in. We become hypoglycaemic when the body cannot use fat to fuel its cells, and ketones to fuel its brain. And the more insulin resistant, the more prone to hypoglycaemia.Moreover, insulin sensitivity, or resistance, exists on a continuous spectrum in the population. It goes from extreme sensitivity to extreme resistance. On the side of high resistance, we have type II diabetics; and on the side of high sensitivity, we have those people like me, and maybe also like you, who restrict carbohydrates, getting most of their calories from fat, and whose cells are consequently fuelled primarily by fat and not by glucose. This makes them, it makes us, not only highly metabolically efficient, but also impervious to hypoglycaemia.This is why I said what I did to my dentist over the phone the other day: for a body whose cells are highly insulin sensitive from being minimally exposed to glucose/insulin in the bloodstream, the levels of which are delicately and sensitively regulated by the liver (glucose) and pancreas (insulin) throughout the day based on food intake, activity and stress levels, the cells are primed to burn fat efficiently, and the liver is primed to produce all the fat-derived ketones to nourish the brain, which they do far better than glucose can. For a body that works like that, it is physiologically impossible to become hypoglycaemic.By the same token, it is also physiologically impossible to 'hit the wall', just because the cells are fuelled by burning fat, not glucose, and there is always a large reservoir of fat in the body, in terms of calories, at least an order of magnitude larger than the reserves of glycogen in the liver and muscles combined, and this, no matter how thin you may be. For example, even at 8% body fat (like me), which is quite low, a person weighing 63 kg (like me), has 5 kg of fat to draw on, providing a reservoir of 45 000 kcal! This is why we see more and more high level long distance athletes and professionals (like this one), and even power lifters (like this one) switching to a very low carb high fat diet (often abbreviated VLCHF). They do this to get lean and to tap into the metabolic advantages of nutritional ketosis.Two final points:1) Insulin sensitivity depends sensitively on exposure to insulin, which depends sensitively on the presence of glucose, which depends sensitively on carbohydrate intake. And it is as simple as this: the less carbohydrate, the less glucose; the less glucose, the less insulin; the less insulin, the more insulin-sensitive. This is always true even if different people have different genetic predispositions to insulin resistance.2) Nutritional ketosis depends on the ratio of calories derived from fat to those derived from carbs, as well as on a specific maximum amount of insulin-stimulating carbohydrates per day. This threshold depends on each person individually. For one person it can be as high as 100-120 g, whereas for another it could be at low as 15-20 g. In addition, if you deplete your glycogen stores from going for a really long bike ride, for example, you can eat as much as 200 or even 300 g of carbs, and still remain in ketosis, because all of it will go to replete glycogen in the muscles and liver. In most people and in most cases, however, a standard guideline is less than 50 g per day. But, remember, the lower the better.So, are you clear on what the deal is with hypoglycaemia? And now, what's it gonna be: carbs, hypoglycaemia, feeling tired and irritable, low in energy and mentally slow, light headed and dizzy; or fats and protein, nutritional ketosis, feeling good and strong, high in energy and mentally sharp, stable and alert. That's a no-brainer, right? What do you say?If you think this article could be useful to others, please 'Like' and 'Share' it.