There are two conditions required for your liver to be manufacturing ketone bodies: (1) you have to be eating very little carbohydrate (i.e., an amount below your individual threshold), and (2) you have to continue breathing in and out.
“Nutritional ketosis” is defined as a serum β-hydroxybutyrate level of 0.5 mmol/dL or above, but even Dr. Phinney, who came up with the definition, admits it’s somewhat arbitrary; it’s just the point at which they started to see some of the benefits of a well-formulated ketogenic diet. Fat- or keto-adaptation comes later, after the muscle cells regain their ability to use fatty acids as fuel in preference to glucose.
But when Dr. Phinney talks about the benefits of nutritional ketosis, he appears to be thinking of things like the reduction in reactive oxygen species, the signaling and gene-regulation effects of the ketone bodies, plus, of course, the healing effect of reducing serum glucose and serum insulin to levels that don’t cause damage. Losing fat is a consequence of these benefits, not a primary effect of a ketogenic diet, and sometimes a body will prioritize healing over shedding fat.
My big concern when people focus on the scale reading is that they have been trained by our euphemistic use of the word “weight” in place of “fat” to think that a lower number is always good, even if it is accomplished by weakening the muscles and making the bones brittler. I long ago made up my mind to be concerned about whether I am losing fat or not, regardless of what number my scale shows me. After all, muscle and bone are denser than fat, meaning that if I grow stronger muscles and bones and still lose fat, the scale number might not reflect how much fat I’ve lost. Fortunately my clothes tell me how I’m doing.
