Really, does it actually matter that something isn't a magic bullet? Either the cost/benefit balance is good enough to warrant doing something, or it isn't. Perhaps taw is overstating the case, and certainly there are other causes of akrasia, but someone giving disproportionate attention to a plausible hypothesis isn't really evidence against that hypothesis, especially one supported by multiple scientific studies.
From what I can see, there's more than sufficient evidence to warrant serious consideration for something like the following propositions:
So, my questions are: If this is correct, what practical use could we make of the idea? What could we do as individuals or as a group to decide whether it's useful enough to bother thinking about? Particularly in cases where willpower is needed mostly to start a task rather than continue it, if there's a simple way to get a quick, short-term boost that might make the difference between several hours of productivity vs. akratic frustration, that's significant!
As an aside, I recall seeing some studies indicating that there may be more general principles in play here, regarding the mind's executive functions as a whole, but I don't have citations on hand at the moment.
I'm wondering if akrasia is partially caused by inefficient use of willpower.
There's considerable amount of evidence that willpower is severely diminished if blood glucose get down, and this effect is not limited to humans. And a small sugary drink at the right time is enough to restore it.
We're talking really small numbers. Total blood glucose of a healthy adult is about 5g and it varies within fairly limited range. Then there's maybe 45g in total body waters. Then there's about 100g of glycogen in liver, plus yet larger amount in muscles and other organs, but which doesn't seem to take part in sugar level regulation. For comparison a small can of coke contains 33g - a really small amounts at appropriate times can make a big difference.
This leads to two issues. First, is blood glucose a good explanation for willpower deficiency and therefore akrasia? I'd say there's significant amount of evidence that some effect exists, but is it really the most important factor? Humans are complicated, science knows very little about how we work, and probably half of what it "knows" is false or at best only half-true. Caution is definitely warranted.
And the second issue - if this theory was true - and by manipulating blood glucose levels you could achieve far greater willpower whenever you wanted, what would you do? It seems that exploiting it isn't that easy, and I'd love to hear if any of you tried it before.