A term which is supposed to refer to a body mass index of less than 18.5 or simply being in a healthy weight range but is overused to categorize what seems like thin people in general.
Ridiculous really, just because someone weighs a couple pounds under the fixed ideal number and is clearly healthy they seem to be branded with a word that makes them sound unhealthily thin.
Meanwhile if someone weighs anything OVER the fixed ideal weight they are never called overweight until they actually reach the BMI 25 mark. In fact, women are complimented and praised for having 'great curves' while if they weigh anything below that optical number they are considered 'fit for eating disorder diagnosis'.
Jim: "Well i guess I'm about 5'8 and I weigh.....150lbs?"
Doctor: "Sweet Jesus. Ideal weight for that height is 155lbs! You are clinically underweight. God have mercy on you Jim. I advise a high calorie diet and intense workout regime. You're body mass index is only 22.8 for heavens sake, build some self contr-"
Jim: "But I -"
Doctor: "Follow the obesity Jim. Being slim and healthy just isn't acceptable for any man Jim. A 33 inch waist is.....unmanly in my opinion. Its just not the American way. EAT! EAT! EAT!"
Jim: "Isn't obesity unhealthy?"
Doctor: "Oh so you're offending fat people now? Get out of my office, you....uh ...perfectly healthy yet underweight twig!".