Aaaaand, we’re back! :)
Yowzer, folks! The feedback from yesterday’s post – an introduction to the world of LCHF and nutritional ketosis (if you haven’t checked it out, you can do so here: http://choosingtoeat.wordpress.com/2013/04/22/get-low-get-low-get-low/) – has been pretty astounding. I’ve had quite a few people get in touch and share their experiences, which I appreciate more than I can say. The shining jewel in my blogger crown? Jimmy Moore – Mr Low Carb himself – shared my post on his Facebook page! I feel truly honoured!
I think, though, that it’s important I point out something here (perhaps something I should have mentioned earlier). The point of this series of posts is merely to describe nutritional ketosis, to give you an understanding of what it is and how it works and why people are so interested in it. At this stage, to be quite frank, I’m not 100% sure how I feel about it. I am planning on doing a post about my own experiences, and where I’m “at” with it all, but I thought it would be a good idea to give you all some background information first. So, I guess what I’m trying to say is please don’t take this series of posts as a blanket advocacy of nutritional ketosis. All I’m hoping to do here is give you a bit of an introduction, in the hope that – if it piques your interest – you have an idea of what you’re getting into and how to go about finding out more.
Alrighty-tighty: on with the show. You’d better strap yourselves in, folks, because today’s going to be a bit of a doozy. I want to try and untangle, in the simplest way possible, the biological mechanisms for the state of ketosis (so, what actually goes down in your body). I am not a nutritionist, I haven’t got any qualifications in this field, and you certainly shouldn’t be looking here for medical advice – but I do want to try and decode this process in plain English, so we can better understand and evaluate this nutritional paradigm. Sound good?
A Brief Reminder
Just in case you’ve forgotten, I thought I’d give a quick refresher: under “normal” circumstances, your body burns primarily carbohydrate (sugar/glucose) for energy. A “ketogenic diet” involves radically reducing one’s carbohydrate intake, to induce a state of “ketosis”, where the liver will begin producing chemical compounds we call “ketones” and one’s body will begin preferentially burning these ketones, and fats, for fuel. This approach is believed by some to be extremely effective for the treatment of many ailments, and also for weight loss, but it is still criticised pretty heavily by most nutritional authorities.
So, with all of that in mind, let’s start breaking this thing down.
What “Normally” Happens
I thought the best way to begin would be looking at what happens with a “normal” or “standard” metabolism – what happens when we eat an average amount of carbohydrates on a regular basis.
Let’s say we eat a “healthy” whole wheat sandwich, with anywhere around 80-90g carbohydrates. We chow down, and the food reaches our gut. All of the digestible carbs (so, all of the carbs, except fibre) are broken down into simple sugars in the intestine. This is what people mean when they say all carbohydrates are sugars.
The sugars are absorbed into the bloodstream. Your body wants to maintain a pretty steady level of blood sugar (a.k.a., blood glucose), so, when it senses the level rising, it signals the pancreas to start pumping out insulin. Insulin is the “storage hormone” – it will send the glucose where it needs to go, and get the blood levels back to normal pronto. If your body has no desperate need for sugar/glucose, insulin will store the surplus of nutrients in the fat cells, which kind of tucks it out of the way for a bit (the way you might hide dirty dishes in the oven when unexpected company arrives).
A few hours later, your blood glucose will start to go down again – this is interpreted by your body as a shortage of nutrients in the blood. The quickest way to get more nutrients? Eat more carbohydrates! So you start to feel hungry, you get the ol’ sweet-tooth cravings happening, and you eat some more carbs…
… and the cycle continues.
And, no, you don’t actually access the excess nutrients that were stored in the fat cells from the original sandwich – it’s much more efficient for your body to get the nutrients it needs from food. However, if you go a little longer without carbohydrates, it will break in to these stores… and that’s where the fun begins! :)
One final point, too: if you eat a meal with lots of fat and protein, but little or no carbohydrate (say, a big plate of bacon and eggs), nothing much happens to your blood sugar. It stays relatively stable, which means your pancreas doesn’t have to send out insulin, and everything cruises along just dandy without any massive spikes.
What Else Can Your Body Use, Aside From Sugar?
There are four main types of fuel our body can use: glucose (sugar/carbs), protein, free fatty acids (FFAs), and ketones. We eat glucose, protein and fat, our liver produces ketones, and we have a few storage systems available to keep some fuel in reserve.
Several factors affect which types of fuels our body prefers to use. Primarily, it is determined by how much of each macronutrient (fat/protein/carbohydrate) we consume. Hormone levels, bodily stores, and enzyme production each play a role – but each of these is, in turn, influenced by what we’re eating. Typically, the body will use a given fuel in proportion to its concentration in the blood. For instance, the more glucose we have in our bloodstream, the more glucose the body will use to fuel itself. If there’s not much glucose around, the body will turn to other sources of energy. Our primary mechanism for determining the concentration of a given fuel in the blood is – you guessed it – what we consume.
And, a quick note on storage, too: interestingly, we can’t actually store all that much carbohydrate, in comparison to protein and fat. A certain amount can be stored in the muscles and liver – about enough to provide us with a day’s worth of energy. But, at the same time, most of us have enough body fat (also called “adipose tissue”) to fuel us for weeks, or potentially months. So, our bodies burn through carbohydrate much quicker – prompting us to eat much sooner.
How Ketosis Happens
When your body is focused on burning sugar for energy (a “glycolytic metabolism”), you will produce minimal ketones, and your body will only burn fat for fuel as a last resort. It should be fairly evident that this is how most of us walk around all the time, when we’re consuming “standard” amounts of carbohydrate.
However, when you drastically reduce carbohydrate in the diet, and your body burns through its (fairly wimpy) stores, something interesting happens: your body starts looking for other sources of fuel, and settles on a combination of fat and ketones. Fat becomes your primary energy source.
When you minimise your intake of carbohydrates, insulin levels go down – after all, there’s no sugar to be stored away or moved around, so it doesn’t have much of a job to do. When this happens, another hormone – glucagon – comes out to play. Glucagon is a “fuel mobilising” hormone – it gets your body to release fuel from storage, so it can be used for energy. This sparks the following process:
So, what we can see here is part of “the Krebs cycle” (the mechanism by which the human body extracts energy from food), when carbohydrate intake is very low. Ketone bodies are essentially by-products of the breakdown of fat in the liver, and they are used alongside FFAs for fuelling the body.
The major determinant of whether the liver will oxidise the FFAs and produce ketones is the amount of liver glycogen present – that is, the amount of carbohydrate stored in the liver. This store needs to be depleted in order for ketogenesis (the production of ketones) to occur.
How Do We Know We’re In Ketosis?
That’s the million dollar question.
“Ketonemia” describes a build-up of ketones in the bloodstream – so, the liver is pumping out enough ketones to increase the concentration of them in your blood. This is the truest indicator that ketosis has been induced. We can test our blood for ketones, in a similar fashion to testing our blood glucose levels – pricking the finger, and whirring the blood through a fancy gizmo.
“Ketonuria”, on the other hand, describes the build-up and excretion of ketone bodies in the urine. This occurs because ketones ultimately accumulate in the kidneys, when they’re not used up by bodily tissues. As such, you can also test your urine for the presence of ketones, which is a semi-reliable indicator that you have entered ketosis as well. However, when your body starts using ketones more efficiently, you will excrete fewer and fewer of them, so they won’t necessarily show up on the urine test. Also, by the time there’s a build-up in your urine, you’ve already been producing ketone bodies for quite a while, and ketonemia has already occurred. In the end, urine tests are less painful, cheaper, and more easily accessible, but not as reliable.
Of course, there are other symptoms of a ketogenic metabolism, and you can look out for those. If you’re closely tracking your carb intake, too, you can make a pretty solid guesstimate as to when you’ve entered ketosis. Though, it goes without saying, that these methods can be a bit hit-and-miss as well.
A Couple of Final Notes
I’ve thrown a lot of info at you very quickly, so I’ll just add a couple more small notes to send you off. Firstly, we need to remember that there will always be a small requirement for glucose, under any metabolic condition – your body never stops using carbohydrate completely. But – and this is a big but – your body can adapt, conserve glucose for where it is needed most (instead of burning it indiscriminately), and it’s very hard to take carbohydrate intake down to absolute zero, anyway (so you’ll still be consuming enough to meet your needs, even on a ketogenic diet).
Your body doesn’t technically require dietary carbohydrates for survival, either – it can generate glucose from other sources, so carbohydrates are not “essential” for this purpose. However, just “surviving” isn’t really the ultimate goal, is it? Whether we need carbohydrates for other endeavours, such as exercise or muscle growth, is a different issue.
And, I’d hope it goes without saying, don’t jump headlong into a ketogenic diet based on this post alone! What I’ve depicted here is the perfect scenario – where a healthy person minimises carbohydrate intake, and induces ketosis. It does not always play out that way, and given how complex this whole system is, there are a lot of ways it can go wrong. We’ll be looking at those more in the near future, I promise.
The Take-Home Message
This post has (hopefully) explained in a little more detail how ketosis actually happens in the body. Essentially, when your liver realises there’s not going to be much carbohydrate around to burn, your body starts breaking down fat tissue, and your liver burns some of it to create ketones. Both the fats and the ketones can be used by your bodily tissues for energy.
Do you feel like you have a better understanding of how ketosis works? What did you think of my diagram? Is this something you’re curious about, or does it sound just a bit too whack-a-doodle?