What’s a ketogenic diet?
A diet is ketogenic when it is very high in fat, high enough to cause a change in your metabolism whereby more fat is turned into ketone bodies rather than being directly oxidized into a form of cellular energy called ATP. Like fats, these ketone bodies (or ketones) can also be oxidized to make ATP.
For this metabolic switch to happen, not only must there be a lot of calories coming from fat, it’s also important that few calories come from carbs and protein (particularly the carbs). This metabolic switch that happens on a ketogenic diet is called ketosis. There isn’t just one specific ketogenic diet.
In fact, you can be on a carnivorous ketogenic diet or one one where most calories are derived from plants. Here are examples of the ratio of dietary fat-to-carbs-to-protein that can induce ketosis.
These percentages of fat, carbs and protein are estimates, not fixed values. Many factors affect what ratios of the macronutrients get one person into ketosis and not another. Not only does does the macronutrient split differ from person to person, a person’s individual circumstance (like sleep, exercise, stress, genetics etc.). can affect it too.
How do I know if I’m in ketosis?
The level at which one is ‘in ketosis’ can be a somewhat arbitrary value. However, there are molecules whose concentration you can measure to set a (somewhat arbitrary) threshold. If you have more than >0.5 mmol/L of a molecule called 𝛃-hydroxybutyrate in your blood, the consensus is that you’re in ketosis . You can also measure how much acetone is in your breath and acetoacetate in your pee. The concentrations at which these indicate ketosis are even less clear .
What’s a ketone?
A ketone is a kind of molecule, a kind of molecule we humans make from fat. Ketones get shipped to mitochondrial machines bathing in oxygen found inside our cells. Once in there, ketones get oxidized to generates ATP. Chemically speaking, the central feature of a ketone is its ‘parent structure’, the double-bond between a carbon atom and an oxygen atom. From this structure, two other carbon-contain chemical groups branching off of it.
When talking about ketogenic diets people often say that ‘there are 3 ketones’. Careful chemists will tell you this is wrong and bashful biologists think it’s right enough. Nevertheless, the 3 common ‘ketones’ are acetone, acetoacetate (AcAc) and 𝛃-hydroxybutyrate (BhB). The latter isn’t technically a ketone (it’s more of a straight chain monocarboxylic acid).
Is a ketogenic diet the only way I can get into ketosis?
There are several ways to be in ketosis aside from a ketogenic diet.
- Be a new-born baby fed breast-milk 
- Fast  (meaning, don’t eat)
- Use up your glycogen by exercising 
- Take exogenous ketones  (pop a ketone pill)
Our history with ketosis – is it unnatural?
Ketosis is simply a metabolic state. It is normal for humans to be in and out of ketosis. During human evolution, there would be times where we’d be in and out of ketosis for many reasons. For instance, seasonal changes often meant sugary and starchy foods were not available year round for our ancestors. An absence of such foods pushed early humans to meet their energy demand with higher-fat diets since dietary energy needs are nearly entirely met by fat or carbs, with protein being only marginally useful for this purpose.
Furthermore, fatty nutrient dense foods like meat, seafood and in particular offal (the weird animal bits like liver), were seen as delicacies  and thus highly prized. Populations living further North had to adapt to less vegetation growing around them and to the kind of animals capable of living in this environment. This meant many human tribes relied substantially more on hunting larger, fattier animals rather than on gathering smaller, leaner game (like birds and insects! ).
Consider this too: all of the essential micro and macronutrients for humans are found in adequate quantities in the flesh of animals, not plants. To successfully nourish themselves, humans had to do so within a framework called optimal foraging theory.
In their case, this biased their food gathering efforts towards foods of animal origin. These kind of foods happen to be low in carbs and thus conducive to ketosis. Keep in mind though that the argument for ketosis isn’t as simple as “we were sometimes ketogenic back in our past so it must be good for us now”. Nevertheless, the story of human evolution does support the idea of ketosis being a normal metabolic state. In other words, it passes the first evolutionary filter.
Do ketogenic diets or ketosis have medical benefits?
Yes. Modern science has now uncovered several good reasons to eat a ketogenic diet. How much time you need to spend in ketosis (and for what reasons) is still an open question. Nevertheless, it has been shown to potently lower inflammation, probably due to its effect on the NLRP3 inflammasome . The absence of dietary carbs and ketogenesis can powerfully lower high blood sugar .
It’s so good at doing this that people taking blood sugar lowering meds need to let their doctor know if they decide to experiment with a ketogenic diet. Ketogenic diets are also known to effectively lower insulin resistance , which is especially beneficial for the obese and diabetic.
Particularly interesting for the obese is the fact that ketones (those molecules produced from fat on a ketogenic diet) can normalize appetite and lessen cravings . More and more cancer research is revealing its cancer-fighting properties . It’s still unclear if it’s powerful enough as a stand-alone therapy for some patients, although the trend indicates a majority of patients will benefit from ketogenic diets (and fasting) when combined with other meds.
One the the first historical uses of ketogenic diets was for epileptic seizure control . Check out the wonderful series of blog posts written on this subject by cancer researcher Dominic D’Agostino and his writer colleague Travis Christofferson . It appears that ketogenic diets reverse symptoms of many diseases, possibly slowing the progression of many of the chronic modern ones .
Don’t I need lots of carbs to exercise?
No. A better question is “Is a ketogenic diet optimal?” Or “Is a ketogenic diet equally beneficial for everyone?” Those are questions we cannot yet answer. But we have some clues. For instance, higher peak fat oxidation rates  have been measured in keto-adapted athletes . It remains to be confirmed whether or not this translates to increases in endurance capacity. Keto-adapted athletes are people who’ve been on a ketogenic diet long enough for their performance to return to baseline following the days to weeks long dip that often happens when transitioning from a higher-carb diet.
In that same vein of exercise questions, people also ask “Won’t my Crossfit workouts tank, bro?” Beyond the transition period, probably not (see our post on carbs and high-intensity training for more).
Ignoring pro or con anecdotes for a moment, there’s no strong evidence suggesting that strength or power losses occur long-term on ketogenic diets. Mind you, strength and power aren’t the same same as ‘glycolytic efforts’. Nevertheless, as we’ve already mentioned, beyond the first few weeks of adaptation to a lack of dietary carbohydrates , there doesn’t seem to be any sustained drop in power or strength . Some high-level gymnasts really seem to love what ketogenic diets did for their performance !
Should I feel guilty about eating fatty foods?
No. Just make sure you eat healthy fats (see our Good fats Bad fats series). Even better, in Nina Teicholz’s book you will find out, in riveting detail, why modern food supplies are filled with unhealthy fats . Despite this unfortunate reality, remember that a big part of life is enjoying food. So…
Enjoy tasty, rewarding, hyperpalatable, hedonic food…that’s healthy – it exists!
After a long day of hard work, enjoy that juicy, rare steak. If you so desire, accompany it with some fresh garden kale with onions delicately sautéed in butter. Maybe you’re feeling more like fish, so feed yourself a slab of poached salmon with olive oil drizzled over a side of sweet & sour peppered cabbage.
Strangely, I often hear that if such meals are indeed healthy, it must be because they’re not that rewarding or not that palatable and thus don’t cause us to overeat. This puzzles me. Speaking for myself, sometimes my mouth waters simply at the thought of them. I genuinely find high-fat meals hyperpalatable, rewarding and get hedonic pleasure from them.
I like Dr.Baker’s quip (@SBakerMD on Twitter). He remarked on how his dogs never get tired of the same old delicious raw red meat he feeds them every day. These animals (whose diet is very similar to our own ) never seem to get palate fatigue. Interesting…
Lastly, get inspired!
– We recommend visiting http://www.ketogenic-diet-resource.com for more information on how a ketogenic diet can help you meet a variety of health goals