The information that willpower is a limited resource which must be managed carefully is very useful, and I think it would change how many people make decisions.
It also has the potential to challenge the popular concept of laziness- if willpower isn't an infinite resource that comes out of thin air than it's not morally wrong to refuse to waste it on something, when you have a more important goal to direct it towards.
However, I think the medical information on blood glucose here is wrong. Metabolically healthy people can eat a reasonable quantity of high glycemic index/load foods, and never experience a low enough glucose crash to inhibit willpower later on even if they decide to transition all the way into a long term fast afterwards. Sure, abnormally low blood glucose inhibits willpower but not within the range of normal healthy glucose fluctuations but only in a person with mild reactive hypoglycemia- usually related to mild insulin resistance.
While a pathological condition, insulin resistance has become almost ubiquitous in the United States in the past few decades (the metabolic syndrome epidemic). Metabolic syndrome/insulin resistance is not actually caused by high glycemic index foods, it's symptoms are simply exasperated by them in the short term. Also, glycemic index of isolated foods is somewhat irrelevant because food combinations have very different combined properties. For example, a baked potato with butter causes glucose levels to rise much slower than a plain baked potato.
I would need to give a lot more information here to fully clarify the evidence behind this position, however it's somewhat tangential to this thread.
I don't think anyone would object if you gave us links and studies to follow up on...
I recently read this book. I've tried to summarize the main points below -- you can read my notes here (MSWord doc). You might also find Derek Sivers' notes useful, which can be found here.
NOTE: The general model of willpower (as a finite resource consumed with use) used in this book does not seem to represent a scientific consensus -- see the comments for more detail.
General Claims
Willpower Depletion
Restoring Willpower
Miscellaneous
I declare Crocker's Rules.
[i] I didn’t see enough evidence to conclude whether the cravings are actually stronger, or people are simply less able to resist them, or both. The book claims that both are true.
[ii] The book seems to imply this mental nagging costs willpower, but I don’t recall it being explicitly stated. GTD is also mentioned, and the lack of Next Actions which one has the materials to execute being included in plans causing people to procrastinate. (p. 79)
[iii] The relevant experiment was conducted in a laboratory, so there is no possibility of the experimental results being affected by the fact that people with more self-control may keep their house cleaner. Self-control was measured in ways like being willing/unwilling to week for a larger sum of money instead of receiving a smaller sum immediately, and choosing healthier foods over sugary snacks.
[iv] I wonder if this means that people are more likely to ignore opportunity costs.
[v] ‘Conserving willpower’ is also mentioned around here, which seemed to imply that effective precommitment helped reduce the willpower costs of overcoming constant temptation by making the decision easier.