This is a more elementary post -- most of my blog-buddies are very familiar with it, but I know we have newer readers who might not be....
The debate about ketones never wants to die! In the time-span between Robert Atkins' introduction to the subject and Jimmy Moore's elaborations, I think the waters have just gotten muddier. The technical writer in me is eager to restate the basics, just so the picture's details are a little clearer and more discernable.
In the early low-carb days there was confusion in the weight-loss world between ketosis and ketoacidosis. Atkins explained how they are entirely different states in more detail, but suffice it to say that a person following HIS DIET could use the pee-strips to determine how well their bodies had learned to burn fat for fuel. Because elevated insulin suppresses fat-burning, a positive urinary ketone reading is a proxy for normalizing insulin levels.
A positive ketone reading on those keto-strips is also evidence that potential-human-fuel is being WASTED down the toilet. THAT may well be the "metabolic advantage" of a low-carb diet: energy -- the metabolic product of fat -- being flushed away.
Atkins saw some obese patients who were not even able to lose well on his basic regimen, so he developed the "fat fast" that would jump-start the process. It was a low CALORIE (approx. 1000) version, designed to force the body to burn adipose tissue because it provided almost no carbs and minimal protein. The "meals" were small but frequent, to help keep hunger at bay. He said to THOSE PATIENTS, if the fat-fast worked for them, they should add one more "feeding" of the same type (so around 1200 Kcal), to see if they were still able to lose weight on that, and if so to morph back into his basic plan -- it wasn't meant to be a long-term eating style.
Decades later when more quantitative measurement (of blood ketones) became available, researchers played with the notion of just how high those measurements would be when their test subjects lost fat-weight most efficiently. The LC-diet world grabbed that ball and ran, not stopping to think that such a number MIGHT be individual and/or particular to the demographics of the subjects. It became the mode to try to emulate THE NUMBERS in that study.
...WHERE HAVE WE SEEN THAT BEFORE??? Oh yeah -- drugging people to raise their HDL, thinking it was a causative factor, not the SYMPTOM of better health that it actually is!
Large numbers on your ketone-meter, or dark colors on your pee-strip, do NOT mean you're losing fat-weight.
I repeat, HIGH BLOOD OR URINE KETONES DOES NOT MEAN YOU'RE LOSING FAT-WEIGHT.
It means your body is converting the fats present in the body into ketones. If you're consuming less energy than your body is burning from day to day, then the ketones are coming from body-fat. If you're eating more than you actually use, dietary fats are available for that process, too, or at least stored as MORE body fat THEN converted.
The reading of ketones is probably most helpful as a surrogate for your insulin levels -- the more ketone the less insulin, and vice versa.
There, was that helpful? :-)