Is Gluconeogenesis Driven By Demand? - Q&A #8

In latin, the meaning of gluconeogenesis (GNG) translates to "creation of new sugar."  In fitness, the term refers to the fate of dietary protein after feeding. The general understanding can be summed up as excess protein turns to glucose in the body. 

You may also be familiar with GNG through my writings on fasting. Here, GNG serves to maintain blood sugar when supplies run low. This is a different discussion relating to body protein, an umbrella term for "stored protein" in tissues like muscle, and the discussion below concerns GNG of dietary protein. Important distinction, that's all.

OK, so a Patron recounted a puzzling conversation resulting in the following statement, “If you only give your body protein post workout, it will break down this protein into glucose via gluconeogenesis.” 

Sounds like a raw deal, but is it true or false? Someone jumped in and gave the wrong answer and that set the stage for today's Q&A. 

Supply or Demand?

The stage was actually set months ago, starting with that dumbass Shawn Baker. He went on Joe Rogan's podcast, threw out a bunch of nonsensical statements, and this bullshit was gobbled up like gospel by the plebs. Leaving me to clean up the mess. 

Among countless falsities, claiming GNG is "demand driven" counts as Baker's more outrageous displays of nutritional illiteracy. Fact you can say that shit without someone batting an eye is...alarming to say the least. 

I've been hearing this nonsense -  "demand driven" - ever since as people shamelessly repeat what they hear instead of thinking or researching for themselves. Time to stomp it out. 

Facts

The amount of protein turned into glucose via GNG ranges from 10-90% in any given meal. 60% is standard. But this is the kind of stuff you know from internalising science and being interested in nutrition, not cherry-picking abstracts hoping no one's smart enough to call your bluff. 

With a cursory glance at PubMed abstracts, it’s easy to come away with the wrong conclusion about GNG. For example, recent work states “Dietary Proteins Contribute Little to Glucose Production, Even Under Optimal Gluconeogenic Conditions in Healthy Humans.” 

In this study, subject consumed 4 eggs (23 g protein) after an overnight fast. 

Meal (low protein)  --- 12 hours (Sleep) --- Meal (low protein): GNG (10%) 

Under these conditions, only 10% of the protein consumed went through GNG. That's only 2 g out of 23 g protein fed. Why so little? Because the extent of GNG is always relative to protein consumed, relative to time. 

Knowing this, the 10%-figure is explained by the following:

• 12 hours or more passed since the last protein feeding. It's also fair to assume a small amount of protein, probably no more than the 23g fed in the morning, was consumed then.
• Egg protein is a notoriously slow protein source. Far slower than casein, for example, and digestion speed affects GNG. The faster the protein, the greater the GNG.  Whey causes staggering amounts of GNG, for example. 
• 8% GNG is the number given in the study but this merely accounts for GNG in the liver. You don't know what I'm talking about, but I rounded the number up for good reason. 

OK, now let’s contrast this to a real classic from '92, “Glucose appearance rate following protein ingestion in normal subjects.” 

Out of the 50 grams protein consumed as cottage cheese, roughly 30g turned to glucose. That's 60% and much higher than the previous study.  What gives?

• The study was conducted at 5 PM with no special directions given to participants. Subjects probably ate a few hours prior, and it's fair to assume a small or moderate amount of protein was consumed at noon, i.e. 20-30 g or so. (Average Joes eating average meals)
• Having eaten protein prior to the test meal, the test meal itself contained a large amount of protein (50 g). 
• GNG increases exponentially with rising intakes. If 23g protein results in 10% GNG, twice the amount doesn't result in 20%. The figure will generally be higher regardless of circumstance. 
• This study mirrors real life situations.

Summary 

What have learned from all this? 

Most of the protein you eat turn to glucose, and to say this only occurs "by demand" betrays a very poor grasp of basic energy metabolism. Where else would the protein go? Guess that never entered anyone's mind...

But wait, what about the guy who claimed protein turned to glucose if consumed without carbs post-workout? More right than anyone else thus far, but he probably didn't know it himself. 

Indeed most of the protein would be turned into glucose and directed towards muscle glycogen stores, just like carbs. But the BCAAs in said protein would increase muscle protein synthesis and do the job protein's supposed to do. Always? Yes, always. (BCAAs aren't glucogenic.)

You now understand GNG better than anyone else out there. As far as its role in postprandial GNG from dietary protein is concerned. Want to learn more and deepen your understanding of GNG and its role in energy metabolism?  Start with a good text book and a thorough reading of Cahill. If that won’t do, the two studies cited here and a romp through their respective reference list might do the trick. 

That’s all folks. Please let me know in the survey if I should bother with this shit in the future. Might be too much science and gobbledygook for some.