I am a truthful person. If a girl is not that good looooking and she is fat i will tell her. I will tell her what her imperfections are. Why is that a bad thing since they want to know the truth secretly and when you tell them its a taboo subject? Can that be detrimental to my game if i tell the truth all the time? How can i sugar coat them?

There is a thin line between being honest and being just plain rude. Your post doesn’t really explain weather anyone actually asked for your opinion or not? This can be detrimental to any relationship you have with people. When you’re straight up like that it shows that you can’t be bothered with feelings of empathy for the person – an essential component of maintaining relationships ( even social animals like mice have this capacity). You don’t have to lie you just have to find the good in your perception as well as the bad. Try to be nice to people when you first meet them, if they rub you up the wrong way then by all means tell them how it is.

_________________
you can fake it till you make it, but if it feels REAL go with the flow!

That's just being socially retarded. When she's really fat, she'll know and there's no point for you to repeat that.
If you want people to respect you, you'll have to respect them back.