Is it true that in terms of biology, fat people are unattractive? Hey guys. So I know that for a fact that most people prefer healthier fit mates. But in certain sources I've heard that being fat or unhealthy in general is undesirable since it could mean bad genes and the ailments associated with it could be passed down to your children, and there's even infertility and birth defects. I would just like some solid proof in case I have to use this in an argument.