I was keeping quiet about this, 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. I'm pointing 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 weight/body fat as they expected & they may even gain.
I don't 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.
EDIT: Here's evidence that dietary fat can be stored in the absence of dietary carbohydrate. It involves doing maths on an Oral Fat Tolerance Test:- On burning, storing and recomposing.
EDIT: Here's evidence that a calorie is a calorie (where weight change is concerned):- Bray et al shows that a calorie *is* a calorie (where weight change is concerned).
As a lot of people report that they can eat dietary fat without getting fat (& actually getting lighter & slimmer), there appears to be something "magical" going on. It's generally accepted that fat is the least thermogenic of all the macronutrients & protein is the most thermogenic. I wonder if this is the case for all types of fat and all types of people.
See Butyric Acid: an Ancient Controller of Metabolism, Inflammation and Stress Resistance.
From 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's Carbohydrate Insulin Hypothesis, everyone loses more weight on low-carb, high-fat (LCHF) diets than on high-carb, low-fat (HCLF) diets. Therefore, Gary Taubes's Carbohydrate Insulin Hypothesis is false.
It's possible that in people who do well on LCHF diets, kcals out on the right hand side of the Energy Balance Equation increase significantly. So keep on keeping on.
EDIT: With the benefit of four more years of knowledge, here's why LCHF & ketogenic 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.
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 & Enzymes.