I have to ask though, why not just eat some carbs, if you're going to get a blood sugar response anyways? What's the biological difference between eating some carbs and having carbs synthesized from protein and fat? Other than the obvious digestive differences.
As long as the carbs are kept to a minimum (50 grams/day or less) there is probably little difference. If carbs make up a significant part of a meal, one difference that is striking is the BG curve after eating. When eating carbs, even carbs with a low glycemic index, BG shoots up rather rapidly probablly causing a large insulin response to quickly reduce the level. When the body must create the glucose from glycerol phosphate or amino acids, the curve is much gentler, the peak far lower, and the duration longer.
My own BG measurements show that carbs will casue a 50 to 100 point rise in BG within the first 15 minutes to 45 minutes (the time depending on the amount and glycemic index of the carb) and it then just as quickly falls, sometimes well below where it started before the meal, indicating to me that insulin was released to rapidly handle the BG spike. I also often feel lethargic after eating carbs, probably due to the dip in BG after insulin has done its work.
When eating only protein and fat, BG seldom rises more than 10 to 15 points over a 3 to 4 hour period and then slowly declines back to the initial starting point without dipping below it. It then stays steady for about 20 to 22 hours before dipping a few points just before my daily meal. This gentle rise and fall of BG over many hours indicates to me that little or no insulin was released to handle the small rise in BG. There is also no feeling of lethargy after eating and I remain alert and can immediately continue whatever I was working on without fatigue or distraction of hunger.
Some of the more current studies have indicated that hyperinsulinemia (too much insulin), causing insulin resistance, is one of the main causes of our modern degenerative and auto-immune diseases like diabetes, rhumatoid athritis, lupus, and a host of others. If our goal is to keep insulin low so as to avoid building insulin resistance, I've haven't found a better way than reducing carb intake to a minimum. I have shredded fingers from hundreds of BG readings to support it. You'll find much of it in my Journal.
Lex