Taubes does actually spend a fair amount of time in GCBC talking about the implications of the “alternate hypothesis” beyond unwanted weight gain. I don’t have my book with me ’cause I’m on the road, but here’s a precis from memory.

Mostly the problems he discusses are around metabolic syndrome and diabetes (easily understood connection) and even cancer and Alzheimer’s disease (potential connection that deserves further research), but he also talks about ways we may be able to understand anorexia and chronic underweight: Just as insulin resistance and hyper insulinemia may contribute in the one case, perhaps insulin oversensitivity etc. could lead to the other. Definitely worth real research, and perhaps even worth personal experimentation with “insulin-loading” on your part if you feel it’s safe.

Of course, given our diet culture, most people wouldn’t look askance at you if you wanted to try and eat more carbs — though they’d be mistaken about your intent! Heck, you could try adding one “100-calorie low-fat snak pak” of Oreo cookies a day, and see if it works to pack on the pounds. :-)

1 – ref. Reinout’s comment, if I remember correctly (from about 30 years ago), lactic acid build-up in muscles is a product of anaerobic respiration:
C6H12O6 → 2C3H6O3 + energy. The 2C3H6O3 is the lactic acid…

2 – I absolutely understand why the vast majority of work in this area looks at the problem of how to lose weight, but I would be so grateful if articles like Taubes’ helped me understand why I seem to have a ‘set weight’ which is off the bottom of the BMI scale. Don’t get me wrong – I’m not fishing for sympathy from those who have the converse problem – just trying to figure out why the only way I appear able to put on weight is to build muscle… which disappears again if I stop the muscle-building activity.

The circulating glucose not removed by the liver is used for energy production in brain, muscle, and other tissues or else is stored in adipose tissue as triglycerides.

(Muscle also stores glycogen; this isn’t covered in the article, but a million and one bodybuilding websites talk about how to increase these stores!)

Also, there’s one subtlety I left out of my post because it wasn’t directly on-topic, but it’s a phenomenon I do find interesting:

[T]he postprandial delivery of glucose into the hepatic [liver] portal system, together with other meal-related events, stimulates the secretion of insulin, which promotes the formation of lipids and glycogen (while inhibiting their mobilization) as well as the uptake of glucose into muscle and its utilization of glucose into muscle and its utilization there.

My personal trainer has showed me bodybuilding books that argue for eating a 4:1 ratio of carbs to protein in the 20-45 minutes right after a hard weight-lifting workout, specifically to spike insulin postprandially for its muscle growth effects. I’m thinking this passage is suggestive of these effects, while also pointing out that they put the body at risk for fattening effects. (I’ve tried the 4:1 thing and found that the hunger stimulation from the insulin is generally too great for me as an insulin-sensitive person, making a mockery of any muscle-growth optimization. :-)

My best guess about “souring” is that this is about training to “muscle failure”, when there’s such a large buildup of lactic acid in the tissues that the muscle gets sort of paralyzed. Here’s one article I found on a bodybuilding site about this phenomenon. Part of the body’s defense of brain energy, and secondarily muscle tissue, involves resynthesis of lactic acid, as this Friedman-Stricker article passage notes:

The pyruvate [pyruvic acid] and lactate [lactic acid] formed from glucose in nonneural [e.g., muscle] tissues are returned to the liver for resynthesis into glucose to be used by the brain…. minimizing the need for gluconeogenesis from amino acid substrates … produced by muscle catabolism.

This suggests, I think, that muscle training doesn’t tear down the tissue for energy, though it is being “used up” in a sense (while giving the body a signal that it should build up the muscle even more next time!). Muscle doesn’t cannibalize itself for the brain’s sake if it can help it.

I hope this helps. Please do share any sources you come across that shed accurate light on this picture.

* Right after meal time is not the right time for your muscles to be really active. They just get some stuff from protein, but the rest of the body is stashing away energy in fat or feeding the brain.

* Normally, your muscles get their energy via intermediary storage: mostly out of your fat.

* In emergencies, muscles can burn themselves up into acids to provide themselves with energy. So what happens to muscles when athletes temporarily overtax their muscles is called “souring” (if I translate the Dutch word correctly) for a very real “acid” reason?