I believe it doesn’t. It does not raise insulin, have calories, or carbs and a glycemic index of 0. I have 2 teaspoons every morning before I break my fast and I have been very successful. 20 pounds down in a matter of 2 months. But everyone is different.
I’ve lost 50+lbs multiple times and remain fat-adapted/in ketosis using artificial sweeteners such as sucralose, aspartame and Ace-K, and those aren’t nearly as healthful and helpful as Stevia has been. Proteins break fasts for autophagy, and since Stevia doesn’t contain protein it won’t break a fast done for that.
Stevia cannot be broken down by the human body. What goes in is very close to what comes out. When passing through the G.I. tract, a part of Stevia is used by bacteria within the gut, the remaining passes through the liver and exits within urine. Unlike sucrose, fructose, or other sugars, the content of stevia leaf extract cannot enter any catabolic pathway, therefore no calories or insulin response.
Allegedly if you were to drink enough of it frequently enough, your body could develop an insulin response to that type of sweetener. It is relatively new and research is still not definitive.