Our bodies are wonderfully flexible machines that can adapt to many different food sources and environments. Many studies have shown that if a particular food requiring a specific enzyme is removed from the diet, then the body will reduce and finally stop manufacturing that enzyme. If the food is reintroduced, the body will not handle it efficiently in the beginning as the necessary enzymes are not present for proper digestion, however, the body will again slowly ramp up the production of the necessary enzymes to efficiently digest that food if it remains a consistent part of the diet again.
I would expect a similar behaviour as far as insulin is concerned. After many years of eating only meat, I'm sure that my body has pretty much shut down insulin production and there is a good chance that upon taking a glucose tolerance test (drinking a glass of pure glucose and then measuring the level of blood glucose over several hours), I'm sure that I would test diabetic also. Since my body hasn't had to deal with large influxes of glucose for an extended period of time (years), I would expect it to shut down production to accommodate only the the very small swings I get eating my all meat diet.
What none of the extracts discussed was what happens to insulin production after giving the body the same amount of time to re-adapt to the high carb diet that they gave to the test subjects (rats?) to initially adapt to the high-fat diet. They seemed to be one-way tests.
Stephen Phinney found the same types of errors in the initial studies done on keto adapting athletes. The researchers would start the test by changing the diet to high-fat, low-carb, and performance would drop within the first week. The researchers would then stop the study because it was clear that a ketogenic diet was bad for athletic performance. The real problem was that not one of the studies ever gave the test subjects enough time on the high-fat diet to allow their bodies to keto adapt. Phinney did run such a test and found that after about 8 weeks the test subjects were back to their initial performance levels but now eating a high-fat diet - their bodies had adapted but it took significant time.
I always look for this bias when I read studies or research extracts and usually find it. The time it takes the body to adapt is also the reason that I don't make rapid changes in my own dietary testing. I tend to stick with things for a couple of months (and often longer) and let the body adapt and stabilize before I make the next change.
Lex
