It is not the intent of this site to provide medical advice. This blog chronicles my fitness and nutrition philosophy based on some combination of my experience, research, and biases. You read, and you decide.

Saturday, April 3, 2010

Ketosis: A Primer

We are interested in being healthy, lean, strong, energetic and athletic. To this end, we want a metabolic scenario in which we have access to the largest stores of energy in the body: triglycerides (stored form of fat). Many of us have more than we need. This has everything to do with hormone balance, which has everything to do with diet and exercise.

Let’s stick with diet for now. If you eat few enough carbohydrates, your body will not be getting enough sugar from your diet to keep blood glucose levels in the desired range. Lucky for us, the body has other mechanisms that can be called upon to maintain serum glucose levels. The backbone of stored fat molecules (triglycerides) can be converted to glucose in limited quantities, but the main source is a process called gluconeogenesis which takes place in the liver. This process involves the conversion of amino acids to glucose. In victims of starvation, these amino acids come from muscle tissue. In low-carbers, these amino acids come from the diet as long as there is adequate protein intake.

So, today I didn’t eat enough carbohydrates to maintain my blood sugar levels without other mechanisms kicking in. As a rule of thumb, this will be the case if you eat fewer than 120-130 carbs per day. Gluconeogenesis ramps up and converts amino acids into glucose in the liver. This process requires energy from fat. Gluconeogensis uses part of the fat, and the leftovers are converted into water-soluble fat molecules called ketone bodies. Ketone bodies act as an energy substitute for a chunk of our glucose needs (not all). So, now fat is being burned as part of the process that keeps our blood-sugar normalized.

Now, you’ll run into plenty of people who will tell you ketosis is dangerous. Usually this is because:

-Almost everyone in our culture eats a surplus of carbohydrates, meaning their bodies are exclusively metabolizing glucose for their main source of energy. Ketosis is seen as an abnormal state, often associated only with starvation.

-There is an adjustment period for the transition from glucose metabolism to ketone metabolism (note: you’re never completely off glucose metabolism; ketones act as a supplement). Short term studies tend to show a substantial decrease in performance in endurance tests. This effect disappears in longer term studies, as explained here.

-Diabetics can go into ketosis even when their blood sugar levels are high, which is not good. My understanding is that since they are insulin-resistant/deficient, the glucose in the blood stream is not being taken in by the cells for energy. A person with normal hormonal control should not experience this. Ketosis is not ketoacidosis. The body eliminates excess ketone bodies through the urine and breath to maintain blood pH levels. This is why you can test for ketosis with urine strips.

-I’ve heard the claim that ketosis causes bad breath. My experience with friends who test positive for ketosis contradicts this. I’ve never noticed bad breath on them, nor have I been told my breath is bad.

Dr. Eades explains these processes in a little more depth (and with a little more expertise) here and here.


  1. Brant

    Thanks for your lucid post on what is arguably one of the most commonly misunderstood areas of nutrition. I have read the articles by Dr. Eades that you linked and have a few questions.

    1. 120 grams of carbs is incredibly low. Looking at the breakfast I just ate (which involved berries, low-fat yoghurt, and a bit of granola) I'd say I'm easily at 60 g already. Restricting myself to within that limit would mean reducing my intake of fruits (especially) and vegetables (trace carbs). In this case, however, I worry about vitamin and mineral balances, since I'm not on any supplements for either. Would this be a concern?

    2. I rely heavily on dairy products to provide a substantial amount of protein to my diet, but these all contain at least milk sugars that add to the carb count. What is the paleo-opinion on whey protein supplements?

    3. You describe a period of adjustment necessary when you initially start ramping down your carbs to get to within the range for ketosis. I assume this depends on how rapidly you ramp down and how well you can stick to it. Is there any way to measure your progress towards ketosis (short of having a breathalyzer)? And how do you know when you've gone low enough and are in the ketosis range?

    4. Lastly, I know you provided the macronutrient breakdown for your diet in a previous post. If it's not too much trouble, could you perhaps also say something about what foods comprised those macronutrients. I'm wondering what a paleo-breakfast would look like (if my breakfast in (1) is going to be a problem).


  2. 1) First of all, remember that most vegetables don't have very many digestible carbs. For example, according to, cauliflower has 2 grams of digestible carbohydrates per 100 grams of cauliflower.

    With regards to vitamin and mineral deficiencies, I'd direct you to Lutz and Allen's "Life Without Bread" (p. 150 has a nice table that lays out the food sources that contain each vitamin). Out of the 13 essential vitamins, only vitamin C is not found in large quantities in animal foods. I'd pick up a copy.

    Noted anthropologist Vilhjamur Stefannson and a colleague, Rudolph Anderson, lived for a full year on nothing but meat:

    Anderson, at least, was under decent surveillance the whole year, and anyways, they both maintained a state of ketosis throughout the year if I recall correctly.

    Your breakfast looks pretty rough. Seems like mostly carbs with a little bit of protein in the yogurt.

    A meal for me might be liver/meat boiled in heavy cream with onions, green peppers, mushrooms, etc. Another favorite is raw pastured eggs (that I trust), heavy cream, and half a banana in a smoothie.

    I take down a lot of cream, a lot of liver, a TON of pastured eggs, lots of meat, fish, a decent amount of veggies, and a moderate amount of fruit. Occasional nuts, but I worry about O3:O6.

    2) I go more for cream and cheese rather than milk and yogurt these days because of the sugar. If your eating meat and fish, etc, then your protein intake should be fine.

    Also, most protein supplements are processed incorrectly:

    The folks at Weston Price do tend to sensationalize, unfortunately, but they do bring up good points most times. I think the bottom line for me is this: I get enough natural, minimally processed protein from real food that I don't feel the need to supplement with more processed protein sources.

    3) Buy some ketostix from a drug store. They test for the presence of ketones in urine. You don't necessarily need to test positive to be in ketosis, though. Ketonurea (ketones in the urine) reflects the fact that you are producing more ketones than you can use. Your body clears them through urine and breath to maintain blood pH.

    4) I'm getting the feeling recently that my caloric intake has dropped from the 4500 I reported earlier. I think this might be due to the fact that I was putting on a few pounds of muscle at the time.

    Anyways, again, foods I eat copiously include: (following should be lightly cooked) pastured eggs, liver, most non-starchy veggies, meat (ideally from a naturally fed animal), fish, heavy cream, cheese

    Foods I eat in moderation: fruits, starchy vegetables, nuts, raw grass-fed milk

    Foods I try not to touch: grains of any kind, trans. fat, isolated vegetable oils, added sugar, preservatives as a general rule

    Help this helps.

  3. Hey Brant - when you talk about isolated vegetable oils... what do you refer to exactly. I have definitely been cooking with olive oil...

  4. Good question, Dina. I might devote a post to basic understanding of different types of fats and some relevant research.

    My biggest issue with vegetable oils in general is the large amount of polyunsaturated fat (specifically omega 6:omega 3 ratios). Most seed oils can't be extracted naturally (like corn, for example. You can't extract the oil without chemicals and machinery, so it's unlikely that our bodies have evolved to tolerate it: Research tends to confirm this in my experience.)

    Olive oil is a little bit different. Olives are fruits, and the oil is easily extracted without industrial technology. Compared to corn, it has more saturated fat, more monounsaturated fat, and less polyunsaturated fat, which is good. However, olive oil still has an unfavorable omega 6:omega 3 ratio.

    Also, saturated fat is more chemically stable (that is why it is solid at room temp.), and less prone to a damaging process called oxidation.

    I cook with unsalted butter, heavy cream, or coconut milk.

    Verdict: Use sparingly. Cooking with it some won't kill you. Olive oil isn't as bad as a lot of stuff out there IMO (like industrial seed oils), but it still promotes an unfavorable O3:O6 ratio, which is pretty important to keep an eye on. I believe olive oil is fairly resistant to heat damage, but I need to double check that.

    Extra reading:

    Olive oil nutrition:

    Corn oil nutrition:

    Weston Price Fat & Oil guide: