According to the sociobiological theory, the reason that good health is universally sexually attractive is that

This is as a result of healthiness is taken into account similar with procreative fitness. Folks that are thought of engaging also are thought to be fertile and can be ready to have additional (and healthier) offspring. All cultures are desperate to propagate themselves as so much as attainable, and having work offspring could be a means for this to occur.

This is because good health is considered synonymous with reproductive fitness. People who are considered attractive are also thought to be fertile and will be able to have more (and healthier) offspring. All cultures are wanting to propagate themselves as far as possible, and having fit offspring is a way for this to occur.