If 'healthier choices' isn't based on science, what is it based on? Why should someone believe you if it isn't based on science? Many people (myself included)

If 'healthier choices' isn't based on science, what is it based on? Why should someone believe you if it isn't based on science? Many people (myself included) read health headlines, read that everything is causing cancer, that everything is simultaneously bad/good for you, and just tune this out altogether. I just rely on normal intuition 'maintain a healthy calorie budget and keep greasy foods to a reasonable level' and treat all other nutrition advice as superstition, hearsay, and noise.