I was keeping quiet about this hypothesis, as it contradicts Gary Taubes, Michael R Eades & Richard D Feinman and Eugene J Fine.
Please note: This post is not criticising low-carb, high-fat diets in any way, shape or form. I'm just trying to point out that if someone on a low-carb, high-fat diet exercises as much gluttony as they want on roast lamb/pork/duck etc, they may not lose as much body fat as they expected and they may even gain some.
I don't particularly want to start a shit-storm, but as I am in the "a calorie is a calorie" (when it comes to weight gain/loss) camp and a lot of the people whose blogs I link to aren't, I need to go public. So, here it is, copied and pasted from the comments section of Diet, Carbs, Fat and Weight Loss, corrected for spelling.
"I would like to propose a theory which explains how fat cells can acquire glucose (& thus correct a deficiency in glycerol-3-phosphate) even when serum insulin level is basal.
Consider muscle cells undergoing anaerobic activity:-
Anaerobic activity is very inefficient and uses pyruvate at a very rapid rate. A deficiency in pyruvate up-regulates all of the up-stream processes, including Glu-T4 transporters so as to maximise pyruvate production.
This explains why resistance training with weights greatly increases muscular insulin sensitivity and why resistance training with weights when depleted of muscle glycogen can cause precipitous drops in blood glucose level.
Ditto for glycerol-3-phosphate in fat cells. In this case, blood glucose level is maintained by the liver & kidneys, which convert the glycerol backbone of triacylglycerols (fats) and other substrates such as lactate, pyruvate & glucogenic amino acids into glucose."
In plain terms what this means is that, like muscle cells, fat cells can acquire as much glucose as they need, independently of carbohydrate intake.
Therefore, if an excess (beyond what the body is burning) of dietary fat is eaten, this can be stored in fat cells even if serum insulin level does not increase.
There. I've said it. I expect comments! Moderation is enabled. All comments that are free from ad-hominem, straw men & other logical fallacies will be published.
As a lot of people report that they appear to be able to eat lots of dietary fat without getting fat (and actually getting slim), there appears to be something "magical" going on. Now, it's generally accepted that fat is the least thermogenic of all the macronutrients (protein being the most thermogenic). I'm wondering whether this is the case for all types of fat and all types of people.
Stephan Guyenet blogged on Butyric Acid: an Ancient Controller of Metabolism, Inflammation and Stress Resistance and Coconut Oil (high in medium chain fats) is also reported as being less fattening/more slimming than long-chain fats.
As Christopher Gardner said in Battle of the Weight Loss Diets: Who's Winning (at losing):-
Insulin Resistant people do better on low-carb high-fat (LCHF) diets than high-carb low-fat (HCLF) diets. Insulin Sensitive people do better on high-carb low-fat (HCLF) diets than low-carb high-fat (LCHF) diets.
According to Gary Taubes' Carbohydrate Insulin Hypothesis, everyone should do better on low-carb high-fat (LCHF) diets than high-carb low-fat (HCLF) diets. Therefore, Gary Taubes' Carbohydrate Insulin Hypothesis is disproved.
It's quite possible that in people who do well on a LCHF diet, kcals out on the right hand side of the Energy Balance Equation increase a lot. So, keep on keeping on!
EDIT: With the benefit of four years of accumulated knowledge, here's why LCHF & keto diets have an advantage for people who have Insulin Resistance. How low-carbohydrate diets result in more weight loss than high-carbohydrate diets for people with Insulin Resistance or Type 2 Diabetes.
More evidence comes to light that fat is not fattening
Is there such as thing as a ‘metabolic advantage’?
Metabolic Advantage of Ketogenic Diets Debunked? An Intriguing Study You Will Want to Read
Is the Fable of Unfettered Fat Burning Derailing Your Low Carb Diet?
See also How stuff works and Enzymes.