answer:It’s cholesterol levels. Yolks in eggs have a high level of ‘bad’ cholesterol (HDL). However, whites have high levels of LDL (‘good’ cholesterol), if i recall, which is a lot of the cause between the constant flip-flop of eggs being good and bad (basically, whether one outweighs the other is in constant debate). I find the best option is just to eat egg whites most of the time, they’re quite good for you, and yolks only on occasion (because the yolks do contain a lot of good protein, i believe). Of course, I’m not any sort of expert on the subject, so take all that with a grain of salt (and the eggs).. As to the limit of two eggs, i have no real clue there. If you’re eating whole eggs I could see that being a bit much for cholesterol levels, but again I’m not really sure.