Friday, March 8, 2013

Protein - 3.2 or 4.0?

I got a question about this sentence:
"Some say an average of 3.2kcal of protein becomes fuel after to losses in hair, skin, nails, and protein spills from urine"

In this post:
Attia & IFIK

If you burn protein in a bomb calorimeter, it shows 4 kcal of energy produced per gram of protein.  However, in a human, protein often goes to structural usage prior to becoming fuel.  And the proteins that go into your hair, nails, skin, GI lining, and other such structural uses obviously never become fuel.  Further, some of the proteins that come back into circulation after serving as a muscle cell can spill into the urine if the dump from damaged muscle is fast/large enough.  Lastly, there're folks that say even protein that goes directly into gluconeogenesis is converted with efficiency loss.  IOW - it's hard to know exactly how much of protein's caloric potential is ever actualized.  So if you care about calories, it may make more sense to use a conversion factor of 3.2 kcal/gram than the 4 kcal/gram that most of us have heard over the years.

Either way, in Attia's case, his moderate protein intake - moderate given his training schedule and fitness goals - shows how little he's consuming in kcal from protein and carbs, and how much more he's getting from fat.  The significance is his weight loss, fat loss, performance, his health indicators are all moving in the right direction, ESPECIALLY compared to his prior days as a high carb, low fat endurance athlete.

This very high fat approach has also worked well for the very public Jimmy Moore, and yours truly.

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