Fat People Privilege is having people believe you when you mention a health problem. I have Hashimoto Thyroiditis but was misdiagnosed with everything from mono to chronic fatigue to depression for years because I never gained any weight.  It wasnt until my eye brows fell out, my hair went grey and thinned, my heart rate was 40bpm and my periods only came a few times a year that I was finally diagnosed properly. If hypothyroidism comes up in conversation most fat women will claim to have it (self diagnosis of course) and deny that I possibly could because I'm slender.  Because it causes weight gain, right?  No, no, no.  It can make you predisposed to gaining a small amount so you have to take that into consideration.  It might make a 200 calorie a day difference. I love watching these lard buckets get angry and agitated that I challenge their tired excuses. I just nod and smile and say "you've done everything to lose weight, is that so?". I must just have a fast metabolism, not that I work 10 hours a day welding, walk at least 10 miles daily and eat a veggie based diet - that has nothing to do with it.