How to cook boneless skinless chicken breast for maximum health/weight loss?

I would like to be able to cook boneless skinless chicken breast and keep it as nutritionally close to plain as possible, but while at the same time making it taste better than plain. I like bbq sauce, but isn't that fattening with lots of calories? I have also heard of marinading in buttermilk, what does that do to the calories and fat? Any suggestions? Keep in mind I'm a very amateur chef