For a comprehensive page on keto-adaptation and performance by the experts visit this page.
According to Owsley “The Bear” Stanley
This is not a dedicated nor complete article, this page is an extract from Owsley’s correspondence with others. See this page for more info.
Keto-adaptation on zero carbs should be complete in 3-4 weeks.
Ketosis is the situation in which ketones are voided in the urine. It takes place within a few hours of blood glucose stabilising and no glucose entering from the diet. At this point many of the body-structures, such as the brain and deep dense tissues like cartilage and tendon will still require glucose and will not take up the ketone by-products of fat metabolism. So the excess ketones are voided and the necessary glucose is obtained from glycerol and liver glycogen. If carbs continue in small amount, this condition will persist. If however carbs do not reappear in the diet, then the body begins to adapt to using the ketones as food hence the term keto-adaptation. During the period of adaptation, energy levels are subjectively low. As the body begins to run most of the glucose-dependent tissues on ketones, energy increases several fold and some additional benefits are realised, such as a lack of ‘hunger pangs’, increased endurance time, increased strength, a feeling of well-being, and rapid bodyfat loss. Keto-adaptation takes time, from a very minimum of about 2 weeks in a very remarkable person, to from three to six weeks in most people. This is a very hard but very important first hurdle to overcome in getting comfortable in the all-meat dietary path.
A person in permanent ketosis will feel tired, lacking in energy most of the time, which is why so many will abandon a low carb diet- raising the carb levels until the ketosis vanishes restores things to the way they were before carbs were lowered. So you see, keto-adaptation is a very different situation to being ‘in ketosis’.
Eating carbs interferes with fat metabolism, so keto-adaptation removes this problem- the ‘wall’.
Ketone metabolism is not a ‘rapid response mechanism’. Full keto-adaptation takes several weeks, and until that has been done, a slowly reducing level of ketones will spill into the urine. Once adapted, the ketones are barely present in the urine, having been used by the body (in place of glucose).
Cold turkey on carbs causes some degree of feeling tired and having low energy levels for a while. This will pass away gradually over a few weeks to be replaced by boundless energy once you have keto-adapted. If you try to taper-off, you simply delay adaptation, how much so will depend on the level of carbs. But be warned, a surprisingly small amount of dietary carbs in some individuals will stop keto-adaptation in its tracks.
A fully keto-adapted person is NEVER in ketosis, which is either a disease condition or something that happens briefly for a short time after eliminated carbs- the period referred to as ‘keto-adaptation’.
Until you are free of carb intake long enough to fully keto-adapt, which takes from 3 to 6 weeks, you will experience a feeling of lower energy. ANY carb intake, no matter how brief, will derail the keto-adaptation process.
Once keto-adapted, your energy levels will seem to go the roof after the fatigue you experience during the adaptation process. Of course the fatigue is constantly lessening each day, but one you are ‘over the hump’ you definitely will know it. It may take only a couple of weeks, but more often it is at least three and in some people (I don’t know why) it may take longer. The slowest adaptation I am aware of took six weeks, but I really think the cause was ‘hidden carbs’, like the glucose they add to ultrapasteurised heavy cream, etc.
Keto-adaptation and ‘being in ketosis’ are two totally different things. A keto-adapted person shows nearly no urinary ketones, hence is not ‘in ketosis’, that condition only occurs at low- not zero levels of carbs, and indicates an inability to utilise ketones as a glucose replacement, hence they are dumped via the kidneys. It gives you none of the benefits of keto-adaptation.
At the high level of 50 gm carb/day, of course the ketones will disappear, that is high enough to prevent ketosis in first place. Lower from 50 to 20, ketones rise than fall some- between 5 and 20 there are some ketones, but only a partial Keto-adaptation, it takes less than 5 gm/day to fully keto-adapt.