
Originally Posted by
dwkdnvr
It's not a question of 'importance', it's a question of role/function.
To make the logic more explicit......
If burning fat is 'stressful' but burning sugar isn't, then that would imply that the body will preferentially burn sugar whenever it's available. Since our glycogen storage is limited, burning it for basal metabolic processes would result in it running out in less than a single day. From an evolutionary standpoint, this makes no sense because the *critical* role that glycogen plays is anaerobic metabolism - i.e. fueling high-intensity activity of a 'flight or fight' nature'. Fat CAN'T fulfill this role. One day without food would leave you glycogen depleted, which is exactly when you're going to need to tap into it to go hunt etc.
So, burning glycogen for basal metabolism would leave the typical individual drained of glycogen unless they could do the modern 'several meals' deal EVERY SINGLE DAY. You have little to no resilience in the face of food scarcity. Leaving yourself drained of glycogen and thus unable to hunt/flee etc is simply not a behavior that would survive evolution for very long.
Thus, the evolutionary viewpoint seems pretty unmistakable - fat is used for fueling basic metabolism since it's abundant and can carry an individual for a very long time in the face of food scarcity, and can do it while sparing glycogen for when it's truly needed.
Having said that, it's pretty clear that Peat and his followers have no interest in this type of evolutionary thought process - they're basing their behavior on observation. That's fine as far as it goes, and maybe chugging high levels of fructose in the absence of PUFA does exploit some otherwise unknown loophole in our metabolic process. It's possible, but my perspective is that we have a rather poor track record at that type of attempt to improve upon or circumvent 'mother nature', and I certainly would need to see a heck of a lot more evidence before considering it valid.