Yes, you can eat some yeast on a keto diet. Even though you need sugar to activate the yeast, there is no more sugar once it has made its effect. What happens is that the yeast feeds on sugar, and it will consume all the sugar, and none will be present in the final keto pizza dough. So if you are craving a puffy, crispy pizza with real bread flavor, use the yeast option, you won't regret it, and your ketosis will be safe!