Ok, so I'm late in finding this......it's from Gary Taubes' book, Good Calories, Bad Calories: Challenging the Conventional Wisdom on Diet, Weight Control, and Disease. I haven't read the book (making a note to see if they have it at our library, or can get it). But, this section of it, makes sense to me (title of post is link to article).
The main thing I got from this is that even though studies have shown, over and over, that exercise doesn't lead to permanent weight loss (even when coupled with restricted calories [and can lead to weight gain]), that is not what the medical establishment or the diet industry want to hear, so they ignore it and continue to trumpet obesity epidemic and tout all their "Follow this diet, do this exercise" and you will lose weight and become the person of your dreams (which dreams they have brainwashed you into thinking are yours, when in reality they are those of the fashion industry and the media).
For me, whatever level of activity a person does is up to her(him). One's level of health is not something that can be controlled all the time. While everyone can make choices about what they eat, how much exercise they get, how much sleep they get (well, that's sometimes easier said than done), you don't always have a choice about what you are exposed to in the course of your daily life. Health is relative. What is healthy for one person may not be healthy for another. To my way of thinking, health is not a moral imperative. It's not something that can have a set standard that every human being can meet, or should have to meet.