Just wanted to get in on this discussion, as it overlaps with what was discussed on a previous Doggy Pound Thread.
First off, Joel, you and I both agree that the terms CHO load, refeed, and overfeed have different meanings. I agree, one is only going to replenish muscle glycogen, the other is going to upregulate leptin for continued dieting, hence, my comment that refeeds are much more “loose” than cho loads.
On the issue of insulin, CHO, and the letpin response, the fundamental question for refeeds/overfeeds is: does lipogenic activity through the combination of acute hyperinsuliminia, and carb and fat excess energy have to predominate for leptin to be upregulated? In other words, what is the feedback loop for the leptin response.
Since leptin’s primary correlation is with subcutaneous body fat (followed by energy balance), one might suggest that in order to “tweek” the leptin response, adipose tissue has to be agitated. Thus, the whole point of a refeed/overfeed is to stimulate the adipose tissue.
However, insulin by itself does have some effect on circulating leptin levels, perhaps without agitating adipose tissue…“Since insulin responses to energy intake precede changes in circulating leptin, insulin is a good candidate hormone to act as a regulator of changes in leptin secretion resulting from alterations in energy intake” (Havel, 2000)…Furthermore (and most pertinent to our discussion) "Recent energy intake also has a major influence on plasma leptin levels. Plasma leptin decreases acutely during fasting or energy restriction, whereas refeeding and overfeeding acutely increase leptin. *These changes are disproportionate to the relatively small changes in body fat induced by these short-term interventions (Dubuc et al., 1998; Wisse et al., 1999).
Thus, as we can see, lipogenic properties need possibly not predominate for a refeed/overfeed to be effective, although one might assume the more they are dominant, the better the leptin response.
In any event, refeeds/overfeeds can be a bit “messy” compared to CHO loads as it is assumed that one will resume strict dieting following a refeed…this is not necessarily the case following a CHO load.
Also, the point the initial poster made regarding glycogen and fat being calories and all calories not being the same…glycogen, once stored in the body (muscle tissue etc.) is not available for usage but for those structures in the body…thus, low level cardio (or any cardio) would promote fat burn following a refeed once liver glycogen is emptied as muscle glycogen can not be used for the cardiovascular portion…Thus, I have always advocated a more “pure” approach to refeeds and Loads. One can still get very lipogenic on a clean refeed if they eat plenty of carbs such that de novo occurs (1000+) (stimulation of adipose cells and anti-lipolytic action will activate long before de novo)…one might suggest that eating this many carbs is tough?..well, if you are truly bingeing, following a sustained period of energy deficit, it can be very easy to do as some of us know. While it is true that a CHO+FAT, or CHO+PRO or all three hybrid can increase insulin responses (in some cases decrease it), one can do very well jacking their insulin through carbs alone. IMHO, save the fat for the resumption of the keto-style diet days, after a washout period of 24-36 hrs, thus not comprising insulin sensitivity due to the change over in metabolic fuels.
I think the distinction made here is very important…and to be honest, I think that one “accident” of the original “anabolic diet” or “CKD” is that people ate too much on their CHO loads, which then stimulated leptin and accelerated fat loss, thus providing the mirage that this style of diet (glycogen replacement) allowed for more optimal training which then accelerated fat loss…People did not know about leptin then, and hell, we are still learning about it now.