This is one of those religious arguments.  There are those that say protein only converts to glucose when needed, and there are others that believe that some portion of all the protein we eat is converted to glucose.  I'm in the second camp as my personal experience supports that some portion of all protein eaten is converted to glucose.

Example:  I eat a mixture of meat and fat that provides 80+% of calories from fat and about 90g protein per day while supplying around 2,000 calories of total energy.  My average blood glucose will hover right around 85 mg/dl.  If my body needed more then it would start sacrificing lean muscle mass or something to create a higher BG level.  But it doesn't do this so it appears that 85 mg/dl is sufficient to meet my body’s need for glucose.  My lean body mass remains stable (based on caliper measurements) as does my weight.  I can eat this high level of fat for months at a time and BG continues to average 85 mg/dl, and lean body mass as well as weight stay stable.  Everything seems to be in balance and happy.

Now, if I reduce the fat level to 65% of calories and raise the amount of protein that I’m consuming to 150g /day, while eating an amount of food that keeps total energy the same at around 2,000 calories, the spikes in BG reach higher peaks after eating, and average BG rises to 100 mg/dl.  If I continue this regimen for several months, everything remains in balance as well, its just that average BG, and the BG spikes after eating are at higher levels.  I don’t seem to gain weight so my assumption is that total energy consumed vs total energy expended is again in balance.

Continuing on with this same line of reasoning, if my body already has a relatively high BG level of 100 mg/dl, then why would BG spike even higher after eating a protein rich meal?  It certainly doesn’t need more glucose.  This could only happen if some portion of all the protein eaten is converted to glucose.

Now I have to ask the question:  If protein is only converted to glucose when the body needs it, and, if my body is happy for months at a time with a BG of 85 mg/dl, then what would cause the rise in BG when more protein is consumed and BG to fall when less protein is consumed?  The only answer that I can come up with is that some portion of all dietary protein is converted to glucose independent of the body’s immediate need.

I also have found that if I increase protein consumption even more (above 150g/day), the glucose spike after eating rises even higher, but average BG tends to stabilize right around 100 mg/dl. This makes me believe that enough glucose is being created to cause insulin to kick in and hold it right at the threshold.  When we eat carbs the glucose spike is huge and rapid, often within minutes of eating.  This causes the body to overestimate the insulin requirement and dump more insulin than is needed.  This causes BG to fall rapidly after the high carb meal and it may fall to such an extent that we start craving something sweet to bring the levels back up.  This is the normal see-saw most high carb eaters experience.  When the body creates glucose from protein, the rise is much slower but for a longer duration, often several hours.  The very slow rise allows the pancreas time to react with the proper amount of insulin and BG is much more stable.  It would also keep BG close to the threshold where the body starts to release insulin.  For me this seems to be right at 100 mg/dl.

It is also interesting that when eating a higher level of protein, BG stays in a very tight range right around 100 mg/dl for about 20 hours per day. The other 4 hours is directly after eating where BG slowly rises then gently falls back to the 95-100 range.  When eating less protein and higher fat, BG averages right around 85 mg/dl but swings up and down much more.  It may drop into the mid 70’s a couple of hours before eating, and rise to 110 for an hour or so after eating and then gently falling back to 80-85 where it stays until a few hours before my next meal.  This makes me believe that 85 mg/dl is below the threshold where insulin is released as it is not being held constant, but swings in gentle curves peaking after eating and dipping before the meal. 

BG also swings much more in response to exercise when protein intake is lower.  If I’m eating the low protein protocol and BG is 85 and I then run a couple of miles, BG will fall during the run by maybe 10 points, and it will stay near this lower level until I eat my next meal.  This makes me believe that there is no excess glucose hanging around and if it gets consumed, then it will stay low, with the body only sacrificing tissue to create more if it is necessary.  This would tend to keep BG at the lower threshold.  If I’m eating a large amount of protein and BG is 100 when I start my run, it is usually still between 95 and 100 after the run.  Again, supporting the idea that there may be an overall excess of glucose when eating the higher protein diet and insulin is moderating it at the higher threshold level.

Here is an entry from my journal where I do some mathematical gymnastics that seem to support that about 58% of all the protein eaten is converted glucose.

http://www.rawpaleoforum.com/journals/lex's-journal/msg3720/#msg3720

This was probably more than you wanted to know, but I wanted to give you as complete and answer as possible.

Lex

I give up, what about it?  

I've found nothing that states that eating meat itself triggers the release of glucagon.  Do you have a resource?

Lex    

 If you are convinced that a significant percentage of the rise in BG after eating a protein rich meal is directly caused by the release of stored liver glycogen, can you demonstrate this either by direct measurement or by inference through a calculation showing how some parameter we can measure tracks closely with the release of liver glycogen stores (or glucagon levels) but would not be affected by the conversion of the dietary protein itself?  In other words, can you disprove the validity of my observations or how I arrived at my conclusions?  
Lex

Lex,

I am convinced of...nothing. Just asking questions and trying to understand.

As glucagon and insulin are both in the blood, especially after several hours of fasting and a protein rich meal, how can one be sure that no break down of glycogen from the liver occurs?
After all, amino acids are systematically converted to glucose after a protein rich meal, at approximately always the same rate, even when BG is not too low.