Weight Loss, Part 2 of 1 Zillion

For a low-carb blog, there hasn't been much coverage to date of obesity and weight loss.  Weight loss is definitely the foremost reason people try such a diet.  A perception of adverse health effects is the main reason others don't try it, and debunking some of those myths is the main focus of the blog.  It's definitely in-scope, though, to explain scientifically why the diet is an effective way to lose weight.

The prevailing - almost unquestioned - theory of obesity and weight loss is a simple thermodynamic equation: calories in equals calories out, the so-called "energy balance".  It makes intuitive sense.  Whatever your caloric intake, what you don't use, you store.  If your output is more than your intake, you tap into your reserves, which are stored as fat, and weight loss is the result.  If you do the opposite, you get fat.  Even this study from 2008, whose conclusion is to confirm the effectiveness of a ketogenic diet, has this to say:

One hears all sorts of fads and fancies in diet suggested for reducing weight. No special article of food has any merit in this regard. Total calories must be reduced.

It's a good hypothesis, and on the surface, our observations might seem to confirm it.  But a growing mountain of research continues to reinforce the success of another, slightly more complex theory involving the intricacies of human metabolism.  I'm going to try to explain it in as much detail as you can digest, linking as always to scholarly literature along the way in case you'd like to dig deeper.

There are two primary fuels your cells can use to produce energy.  The first is glucose, a very simple carbohydrate.  Glucose is mainly produced by breaking down more complex carbohydrates, which are in your diet in the form of grains, potatoes, sugars and so on.  Once your digestive system has extracted this usable fuel from what you've eaten, it enters the bloodstream.

Here, things get a bit more complicated.  Nearly every cell in your body has everything it needs to take in glucose and get energy from it, but very few of them can do it without insulin.  Your muscles, for example, are the main consumers of glucose in your body, and those cells require insulin to even allow glucose to penetrate the membrane to enter the cell.  Fortunately, certain cells in your pancreas are able to sense glucose in your bloodstream and produce insulin in response.  The more glucose in your blood, the more insulin is released.  This is how your body manages blood sugar levels: blood glucose signals your pancreas to produce insulin, and insulin signals the rest of your cells to consume the glucose.  More on this later.

If there's no glucose in the blood, there's little to no insulin either.  And if there's no insulin, glucose can't be metabolized.  People who can't produce insulin have type 1 diabetes and must inject insulin to manage their blood sugar.  So, if there's no glucose and therefore no insulin in the blood, what do your cells use as fuel?  The answer here is, basically, fat.

Before we get to fat metabolism, we need to talk about how and why fat is stored, since this is the essence of weight gain.  Allowing your muscle cells to use glucose is only one of many functions of insulin.  Another is signaling your fat cells to store fat.  Since we know that there's no insulin in the blood if there's no glucose, and there's no glucose in the blood if you're not eating carbohydrates, it is impossible to store fat without eating carbohydrates.  There are actually other reasons this is true, but I'll discuss those in another article.

As I said, if there's no insulin in the blood, your cells burn fat (usually in the form of ketones and fatty acids.)  You always have some fat circulating in the blood in one form or another, but it cannot be used by most of your cells if there's so much insulin in the blood that they're busy working to get your blood sugar down.  You see, high blood sugar is dangerous, which is why type 1 diabetes is so tricky to manage - the diabetic body is unable to manage it as a normal body would, and if the sugar is allowed to accumulate in the blood, well, things get bad.

Excess ketones in the blood are entirely different.  You're able to simply excrete them in your breath, sweat and urine.  And your cells don't need any special signals to metabolize them - that's the default, as long as there's no insulin forcing them to use glucose instead.  So, if you're not eating carbohydrates, there's almost no glucose in the blood, therefore there's almost no insulin, therefore your cells burn fat, and any excess fat is simply excreted since (without insulin) it can't be stored.

I've explained now why it's impossible gain weight without eating carbohydrates, but how does such a diet help you lose weight?  I've mentioned that insulin forces cells to use glucose as their exclusive fuel, overriding any other factors.  Similarly, it forces fat cells to store fat, regardless of any other contradictory signals they might be getting.  For example, the hormone epinephrine (also called adrenaline) tells your fat tissue to mobilize its fat stores, because you're probably about to need a lot of energy.  Insulin tends to override this.  In fact, there is a large number of hormones that stimulate the release of fat stores (without insulin), and you can learn a lot about that here.

Exercise causes a complex and interesting cascade of hormonal responses, many of which play important roles in the release of fat from the fat tissue.  One of these responses is that your insulin levels are lowered almost immediately, which is necessary for the other hormonal responses to work.  If you're on a ketogenic diet, though, you don't have the insulin obstacle to overcome: your fat cells immediately start releasing fat into the bloodstream to be burned as fuel, and if you don't use it all up, you simply excrete the excess - since, again, you can't store it.

So by eating a ketogenic diet, you have guaranteed that you at least can't put on weight.  Any exercise you do is now far more effective, because fat is released more quickly and can't be re-stored if you fail to use it up.  And whether you know it or not, you're already doing enough exercise to lose weight by changing nothing but your diet.  I'm a programmer of all things, and on top of that I work from home, often from my bed, and I still lost 30 lbs. in the first six weeks of the diet, doing no more exercise than going about my daily, mostly sedentary, routine.

And here's the kicker.  Calories don't matter.  You eat as much as you want, and as long as you don't eat carbohydrates, your body literally throws away whatever it doesn't burn for fuel.  And your fat tissue leaps at the slightest excuse to unload stored fat, because there's no insulin telling it not to.

At this point I can think of exactly three reasonable excuses not to be considering a low carb, ketogenic diet.  The first one is, you get diet advice everywhere you look, and this is just another gimmick or "fad diet".  To that I would say, do your research.  Nothing I've said in this article is controversial other than my unabashed recommendation of the diet.  I've oversimplified here and there, but human metabolism is pretty well understood, and all the physiology in this post is easy to confirm on your own, if you don't believe me or the resources I've (painstakingly) linked to.

Another perfectly understandable excuse is that you're concerned about adverse health effects.  Well, that's what most of the rest of my blog is dedicated to, and in those articles you'll find even more links, to even more peer-reviewed scientific literature to back up my claims.

The last is that you just don't think you can do without carbs.  You love pasta, or bread, or cheesecake, or all the above.  Look, I'm Italian!  If I can live without pasta, so can you.  OK, that's a simplistic answer, and I'm mostly kidding.  The real answer is that you are addicted to carbohydrates, and the good news is that it's a surprisingly easy habit to kick.  The first few days are rough, but you'll find that your cravings just go away after a short time.

I'll close with some bonus citations of medical literature for further research:

• Effect of 6-Month Adherence to a Very Low Carbohydrate Diet Program 
• Effects of a high-protein ketogenic diet on hunger, appetite, and weight loss in obese men feeding ad libitum  
• The Radical Cure of Simple Obesity by Dietary Measures Alone
• Effects of Fat on Insulin-stimulated Carbohydrate Metabolism in Normal Men  
• Hormonal regulation of lipolysis in adipose tissue