Both explanations they give are actually technically true (well, the fat burning thing isn't exactly true because very little fat burn is localized, but when working out women usually lose fat on the bust and hips first, so it ends up being true anyway), but the effects are miniscule unless you are doing something fairly atypical (in the fat burning case, that would be doing actual exercise and in the hormone case, that would be taking large amounts of artificial hormones).
