Easiest is still as subjective as it gets. I never smoked. So, I could say not smoking is the easiest thing. I haven't drunk alcohol in years. So, also more easy than loosing weight. And so on.

Swap "easiest" for "simplest" and it's more accurate to what OP was trying to convey. Literally all you have to do is eat less, that's it. Of course, that's not easy for everyone but it sure is simple.

Simple->complex is orthogonal to easy->difficult.

Stress and mental illness is as a pretty big factor in health degradation. Reducing that by just not dieting seems to me to be the simplest and easiest at the same time.

To each their own, there's a lot of ways to look at any single situation.