Skeletal Muscle Catabolism Decreases During Fasting

Well this is interesting… I just found this on another forum and hadn’t heard of this before. I want to hear your thoughts on this.

Since recent studies have indicated that measurement in urine of the amino acid, 3-methylhistidine, accurately reflects the extent of muscle catabolism, and because it has been suggested that thyroid hormones may influence muscle breakdown, especially during fasting, the effect of T3 and reverse T3 (rT3) administration on the excretion of 3-methylhistidine was examined in obese subjects during fasting. The mean (± SE) 3-methylhistidine excretion in patients fed an egg protein diet (devoid of meat protein) was 256 ± 35 μmoles/day and decreased to 190 ± 14 μmoles/day during fasting. T3 administration (100 μg/day � 5 days) increased 3-methylhistidine excretion to 304 ± 37 μmoles/day during its ingestion and to 485 ± 46 μmoles/day in the T3 posttreatment interval. T3 doses of 10 μg every 4 hr (q4h) for the first 6 days of fasting also appeared capable of increasing 3-mehis excretion whereas 5 μg T3 q4h administered during the first 6 days of fasting did not increase 3-mehis excretion. Reverse T3 administration (80 μg q6h) during fasting was associated with a mean 3-methylhistidine of 130 ± 13 μmoles/day, a value no higher than in patients fasted alone. These observations suggest that: (1) skeletal muscle catabolism decreases during fasting; and (2) pathophysiologic doses of T3 (60 μg/day or more), but not reverse T3, enhance muscle catabolism during fasting.

http://www.sciencedirect.com/science/article/pii/0026049579902063#

Here’s one thing I don’t understand (and haven’t investigated): what does “fasting” mean? Is there some certain threshold point at which ones goes from just not eating to “fasting”?

[quote]DoingWork421 wrote:
Here’s one thing I don’t understand (and haven’t investigated): what does “fasting” mean? Is there some certain threshold point at which ones goes from just not eating to “fasting”? [/quote]
When you wake up and haven’t yet eaten you are in a fasted state. So when they ask you to come in fasted when getting bloodwork they’re just asking you not to eat anything from the moment you wake up until you’ve had your bloodwork

I am willing to bet money that the study defines “fasting” as the term is used in this analysis. Technically, any time between feedings is fasting. So, whenever discussing 'fasting," the time intervals or protocol has to be clearly defined.

[quote]myself1992 wrote:

[quote]DoingWork421 wrote:
Here’s one thing I don’t understand (and haven’t investigated): what does “fasting” mean? Is there some certain threshold point at which ones goes from just not eating to “fasting”? [/quote]
When you wake up and haven’t yet eaten you are in a fasted state. So when they ask you to come in fasted when getting bloodwork they’re just asking you not to eat anything from the moment you wake up until you’ve had your bloodwork[/quote]

Right, but what I’m trying to get at is whether there is some physiological threshold point at which one is actually considered “fasted.” For example, it could be the point at which all calorie-containing materials have progressed past a certain point in the digestive tract or something like that. The whole “well, when you wake up and…” stuff is highly imprecise. For example, what if I ate a ton of food up to midnight, went to sleep for four hours, woke up and got a blood draw. Is that “fasted”?

I couldn’t find the whole study just the abstract, maybe the whole thing will explain it. Also, there’s probably a standard for what a “fasting” state exactly is in these studies so if someone knows that standard then we might be able to assume it’s being used here. I have no idea though, that’s why I want to hear more from you guys. At least from what is shown here, fasting might not be so bad.

Lyle McDonald wrote about this. Initially, yes, muscles are spared and body runs on ffa and some glycogen. But that doesn’t last longer than a ~week or so, especially in lean individuals and those who engage in any intense physical activity that requires glycolysis. In both instances fats become an inefficient fuel and muscles get cannibalized. And both instances apply to us folks (bodybuilders, physique etc.)

This is why the leaner you are, the more carbs and/or more frequent carb-ups you need to keep the thyroid from crashing after 5-7 days. As well as the reason you see higher protein intakes on low carb cutting plans…to convert some of them to carbs.

The point is, there’s no going around a slight deficit and then making up the difference with some exercise. If you cut your daily calories too low, it’s muscle wasting time, fasting or not.