I'm sure a lot of them are just outright lying, they know they eat like crap but they say they don't so that when someone suggests they eat more healthy food they can claim they already are. But I'm sure some of them actually believe their own bullshit. They order a salad with a half pound of shredded cheese and quarter gallon of ranch dressing and the equivalent of a loaf of bread's worth of croutons and think at healthy. Or they try to convince themselves that pizza and burgers are healthy because they have vegetables on them, or that ice cream is a dairy product, and that dairy is an essential food group therefore it's ok for them to eat it.