What is ketosis, really? And how does it impact the body?

Ketosis has gained rapid popularity in the mainstream, especially with the growing number of specialists that are catching on to the fact that added sugar, not dietary fat, is the public enemy number one when it comes to health.

There are pictures of amazing changes in body composition.  There are lavish claims that you "think clearer" when in ketosis.  There's even talk of anti-cancer possibilities.

All three of the above are true, if you do ketosis right.  But the problem becomes the same as most health fads.  A very specific diet spins-off into gimmicks and the usual army of health celebrities hop on board.  Overnight another fifty books by celebrities hit the shelves.

So, to get down to brass tacks, what is ketosis and what can it do for us?


Ketosis itself is a measurable blood level of "ketone bodies" which are the metabolic products of fatty acid oxydation a.k.a. lipolysis a.k.a. fat burning.

The body is always using a combination of fuel sources for energy.  This depends on lots of factors but the simplest solution is this:  Whatever nutrient you are getting the most of is the one your body will prefer for food.  From an evolutionary standpoint this makes perfect sense; your body's energy system must adapt to the environment.

So if you eat more carbs (sugars) like the majority of Americans do, then your body will be in an environment of glycolysis which is the breakdown of glucose (sugar).  There are two types of glycolysis: aerobic and anaerobic.  These types are not of importance here.  

Ketones are byproducts of fat breakdown for fuel.  Simply put, in a situation where there is no glucose ready available, the body will shift to fat burning mode.  Protein may be used as well but the body never really adapts well to protein as a main source of fuel.  Protein tends to "burn dirty" and releases more free radicals.  It is not very efficient.

Fatty acids, however, are the preferred efficient fuel source for the body.  Not only are there more calories to be had per unit weight (9cal/gram as opposed to 4cal/gram for protein and carbs) but our bodies naturally have a high quantity of this fuel in the form of body fat.

So in theory, during ketosis where there are measurable amounts of ketones in the blood, your body will be in a state of efficient fat burning for fuel.  And common sense would tell us that those stubborn fat stores will start to melt away over time.  After all, the fat has to come from somewhere.

And this is basically correct.


True ketosis does involve blood tests.  Otherwise you can think you are in ketosis while you are not, even if you are on a severely limited carbohydrate plan with plenty of fat.  The problem is that it doesn't take much at all to get right back out of ketosis. 

For instance even cutting out all starchy carbs isn't always enough.  If your protein intake is too high, you will still break some of that protein down into sugar (gluconeogenesis) and your body will respond similarly to if you ate something sugary.

For this reason, a high protein diet is not conducive to ketosis as otherwise it might seem that it would.

The real idea is to drastically increase the healthy fats in the diet along with sufficient protein while severely limiting sugary foods.  For the most part vegetables are ok as they are less caloric, but some veggies can still bring us out of ketosis, such as carrots.  

The key to getting into ketosis is thus two fold: How do I drastically increase fat (I personally shoot for 1 gram of fat per lb of lean mass or 150 grams per day) and get sufficient protein without slipping in those "hidden calories" and sugars that seem to be everywhere these days.

Here's a list of acceptable ketosis inducing foods:

- eggs (organic)

- meat cuts (organic)

- butter (organic)

- Greek Yogurt (not low fat)

- olive oil

- flaxseed (solid not oil)

- cheese (organic)

Notice how most of these choices are animal products.  It is possible to get into ketosis on a vegetarian or vegan diet but the glaring problem is this: Vegetable based foods rarely offer significant amounts of fat or cholesterol which are crucial for hormones and ketosis in general.  Just eating tons of vegetables therefore is not a viable solution.  

And to bounce off that last statement, it is also not advisable to use plant oils to supplement your fat.  Vegetable oils are notoriously high in rancid and hydrogenated fats due to processing.  


I personally use a pseudo-ketosis nutrition plan.  What that means is that I lean heavily towards fat as a fuel but I would be a fool to convince myself that I'm truly in ketosis due to the carbohydrates I do eat.

From a health perspective ketosis is superior to most methods.  Fat is a "clean fuel" which is very efficient.  It also doesn't cause the insulin spike that is associated with sugars so it is ideal for diabetics and pre-diabetics.  WIth this reduced insulin spike comes more satiety and less hunger cravings.  Smooth and consistent energy levels are the result.

Then there is the more pressing matter of ketosis and its implications for disease, which would be the best reason to use it in my opinion.  Overall health and longevity trumps short term physique goals.

The idea that cancer tends to grow in acidic / hypoxic environments is very old.  It is believed that the cancer cells are able to grow because they are "starved" of oxygen which the mitochondria uses for energy to burn fat.  The cells are forced to use anaerobic fuel systems because of the lack of oxygen.  Oxygen tends to "alkalize" cellular environments.  So for the most part our acidic and sugar laden diets are detrimental to mitochondrial function and this could cause cancer.

Ketosis naturally combats this acidity and there have been many anecdotal situations where ketosis was claimed to reverse cancer.  Generally whatever reverses cancer also helps prevent it in the first place!

The last benefit we'll use here is the effects on brain fog / concentration.  People in ketosis swear that they are "thinking clearer" and are suffering less mental damage including depression and anxiety - both linked to high sugar diets.  

The reason is that ketones are ideal brain fuel.  They are readily accepted and despite the sugar industries failed attempts they have been unable to prove their use in the diet.  The old claim was that your brain could only use glucose for fuel.  It turns out this was just a crummy commercial for Big Sugar to claim relevance.  

One of the side effects of increasing fat in the diet is that hormones are easier to create, and with increased cholesterol and fat, there will be optimisation of the systems that rely on fat: the nervous system which is comprised of myelin (fat insulators) and the brain in general which requires cholesterol and omega-3 fats.

So in the end ketosis is more efficient, creates less toxic residue, is anti-cancer and helps people with brain dysfunction.  Its pretty hard to argue that this is all just hooplah from the ketosis community.

One word of caution:

Ketosis is admittedly not a long term diet.  It is usually something that is done as a "cycle" to lose bodyfat and detoxify the body.  Long term and / or improperly executed ketosis without supervision can create something akin to anorexia (ketoacidosis) and starvation, neither of which is truly ketosis but can damage the body.

Ben Hetzel

Sports Nutrition Specialist