Hi Jeff! You're welcome to lurk here any time.
Taubes states on page 387 of GCBC That.....
"Some triglycerides in our fat tissue come from the fat in our diet. The rest come from carbohydrates, from a process known as de novo lipogenesis, Latin for 'the new createion of fat'"
He goes on to state that lipogenesis can take place in the liver or the fat tissue itself, and that Glycerol Phosphate must be present to bind the fatty acids into a triglyceride or they can't be stored. Fat is also stored in the form of triglycerides in the fat cells and not as free fatty acids.
Most of Taubes' illustrations are based on glucose metabolism in support of his point that carbs are the main contributor to excess body fat, however, he makes it clear that dietary animal fat is in the form of triglycerides so by consuming it we provide a source for Glycerol Phosphate that is not directly related to glucose metabolism.
This would lead me to conclude that it is possible to gain weight if the diet is extremely high in fat for an extended period of time which is exactly what I experienced. There is also evidence from epileptic children put on an extremely high fat diet, (85% to 95% calories as fat), that research has found that this extreme level of fat is necessary for the children to continue normal weight gain.
My experience was that weight gain was slow. It took several weeks before I noticed it. I also found that cutting dietary fat back down to my original 65% range caused weight to start dropping again. Activity levels also played a significant role. As I increased my exercise, (jogging), it took higher dietary fat levels to maintain the increased weight.
Another clue in Taubes book is that apparently AGP can be burned directly as fuel in some cells. It may be that it is the AGP in the dietary fat that is providing the mechanism to add body fat, but since AGP is also a primary fuel source, it must exceed some threshhold before there is a sufficient surplus to allow the formation of additional adipose tissue. This would explain why I didn't gain weight when fat was 65% of calories, but did gain weight when fat was increased to over 80% of calories.
If AGP can be directly used as fuel it would also explain why weight started to fall when a very modest amount of exercise was added. It wasn't because there was a dramatic increase in burning calories, but rather the specific burning of excess AGP released from dietary fat, making it unavailable to contribute to creating new, or maintaining existing, body fat. If there is any truth to this idea then it supports the "calories don't count" theory.
Of course all of this is just speculation, but the pieces do seem to fit - at least within the boundaries of my limited level of knowledge. Any thoughts on my mental meanderings?
Lex