Different ways to be in Ketosis
- Be a new-born baby reared on breast-milk 
- Don’t eat, use a diet that includes fasting 
- Use up your glycogen by exercising 
- Eat a high-fat diet , low in carbs with moderate protein
- Take exogenous ketones  (aka ketones in a pill)
Ketosis is a metabolic state. It is normal for humans to be in and out of ketosis. Once your body starts relying on lots of fat for energy you get into ketosis. So why isn’t it called fatosis? Because when your body burns lots of fat it also turns some of that fat into ketones which then go on to be used for energy too.
Is ketosis good for human body?
During human evolution, we were probably in and out of ketosis. For instance, seasonal variation for our ancestors often meant little to no sugary and starchy foods which pushed us towards a higher-fat diet. Fatty nutrient dense foods like offal (the weird animal bits such as liver, tongue etc.) were seen as delicacies  and thus in high demand.
The further North a population lived, the less vegetation was available which meant humans relied more on hunting large animals and gathering small ones (like eggs or insects! ).
All of the essential micro and macronutrients for humans are found in animals, not plants, which directs human food gathering efforts towards animals (whose meat is low in carbs). Although the argument for ketosis isn’t as simple as “we did it back then so it’s good for us now”, the story of human evolution supports it being a normal metabolic state. In other words, it passes the first evolutionary filter (see more: Do ketogenic diets have a place in human evolution?)
Ketogenesis as medicine
There are many reasons to be in ketosis given to us by modern science.
- Lowering inflammation 
- Lowering high blood sugar 
- Lowering insulin resistance  (especially for the obese and diabetics)
- Cancer-fighting action 
- Seizure control 
- Increased fat oxidation capacity …and many others.
Sounds good but…. bro, won’t my Crossfit workouts tank?
Probably not. Beyond anecdote, there’s no strong reason to be concerned about losing strength and power. Beyond the first few weeks of adaptation (see more: Are low-carb diets good for high-intensity training?)  there don’t seem to be any sustained  performance drops. And look, gymnasts love ‘em some keto .
Leaving aside the medical and performance reasons to be ketogenic, you may simply enjoy ketogenic foods. Remember – high in fat and low in carbs! For instance, what about a rare steak accompanied by kale and onions sautéed in butter? Or a slab of poached salmon with olive oil drizzled over a side of sweet & sour cabbage?
Tastes good to me!
A note of caution: if you go ketogenic while taking meds to lower your blood sugar or blood pressure you may need to adjust the dose (or stop taking them all together). So talk to your doc. This speaks to how powerfully a ketogenic diet can reverse symptoms and slow the progression of multiple modern diseases .
With that caveat in mind, try eating only those kinds of meals for a few days in a row, you might be pleasantly surprised.
Go read up on ketosis, because next time we’ll talk about the importance of food quality, specifically good and bad fats (see more: good fats vs bad fats series), because knowing which ones to include and avoid matters all the more in high-fat diets.