KFC chicken is just basically chicken with other secret ingredients and those other ingredients which are unknown may not be the healthiest.
Chicken cooked at home is usually the healthiest chicken but even when you eat KFC chicken it's not all that bad health wise.
Still I've known some people who ate a lot of KFC chicken and when I say they ate the KFC chicken I mean they ate nearly nothing but that chicken.
And when they did eat that much KFC chicken those people really gained a lot of weight when they did eat it.
KFC chicken is fattening for a lot of people so as long as you eat the chicken in moderation from KFC then you should be okay.
But eating too much of the KFC chicken could cause lots of weight gain and lead to diabetes, heart attacks, strokes etc.
But that goes for any other food as well that is high in fat content.