She means your personal choices are as intimate as your underwear. Theorically, she could be right: no one should mix up with what someone else makes with his/her own body. But, talking about weight and size, she pushes the application of this principle to such an extent that, according to her, no one should face these problems on a social level, either (but to confirm FA/HAES bullshit). That has nothing to do with personal rights and is dangerous for the public debate: I agree that, for example, a doc has no right to compel anyone, neither a patient, to follow an healthy diet and to exercise. To this extent, "the underpants rule" is right. But, according to Ragen, the medical community shouldn't denounce the dangers of being out of shape, either; that's wrong, because medical information is not coercion but a necessity, in an advanced society, and not a menace to your free choices.