“Healthy weight” isn’t a real thing.
In that, some people are skinnier than is good for them or fatter than is good for them, but: it’s not actually possible to determine from the outside what a healthy weight is for someone, not in pounds or kilos, not in BMI.
It’s possible, and good, to take a weight-neutral approach to health.
There’s plenty of health markers other than weight. Some can be measured by medical professionals, some can be measured by you. (Like how long it takes you to catch your breath after climbing a flight of stairs.) If you want to be able to run faster or lift more or not feel wiped after a grocery run, those are goals you can go after, without paying attention to your weight. (And without dieting ffs.)
Or if you want to lower your chloresterol or your blood pressure or that blood sugar measurement for diabetics. Me? I would, as usual, like lighter CFS symptoms and more activity tolerance. I’d like to be able to do a grocery run without feeling wiped for the next few days. Will I get that? Who the fuck knows. Does my weight have anything to do with that? Not really!
People with my illness do often gain weight. Because of the inactivity, becaude of the difficulty preparing food, because of the poverty that often comes along with chronic illness. (Possibly sometimes because they actually have a misdiagnosed thyroid disorder.) But. There’s people heavier than I am who are healthier, even if they don’t have proportionately more muscle mass, and people lighter than I am who are less healthy. If “healthy weight” was a thing, wouldn’t it mean all people who are at a “healthy weight” are healthy?
I know it’s not meant to mean that. But ... we talk about “healthy weight” sometimes like it’s the only thing that matters, rather than at most being something like “healthy skin” or “healthy lungs”, at most one aspect of the broad spectrum of health and disease.
If you could even tell what a healthy weight for someone is, based on the numbers.
(Why does this matter? In intuitive eating support groups, you’ll always get someone who says “I know I’m above my set point...” no, actually, you do not know that. Because you can’t determine your healthy weight or your set point by crunching numbers.)