I have seen a significant blood glucose drop (indicating an elevated insulin response) in myself and several of my patients after consuming stevia (as well as all the other "natural" noncaloric and/or low glycemic sweeteners such as erythritol, xylitol, monk fruit (luo han guo), Truvia, Better Than Sugar, etc.) So my feeling is that if one is really concerned about repairing their insulin sensitivity and are willing to forgo all sweeteners, they'll get better results. BUT, compliance is definitely an issue for many. Better to use these sweeteners and make slower progress than not do keto at all and make minimal or no progress!!