Um... I'm going to treat this as though you're serious. You're probably wrong here. Lettuce especially is pretty lacking in nutrients, and all of the good stuff in kale is locked inside thick cell walls that have to be broken mechanically or by heat. Moreover, you're assuming that someone is fat specifically because of chips, when they probably make a number of unhealthy choices that cumulatively lead to obesity. I'm not sure a 1 to 1 swap of kale for chips buys you much more than a sore jaw and very regular bowels.