BMI and the whole diet industry is such a con.
BMI was brought in to replace height/weight charts and was meant to be done using calipers and skin-fold measurements. Instead, it's now a height/weight chart hiding under a number.
Everyone loves to bang on about how good it is to diet to an arbitrary weight - and how bad it is to have an eating disorder. But no-one ever seems to make the link between the two, or realise that dieting just gives people eating disorders on top of their obesity (or temporary weight loss - and the VAST majority is temporary)
People with weight problems have issues with food that need to be addressed, because diets don't work - having been on one my whole life, the second I've begun to eat normally I've piled on the weight, because yes, my metabolism is screwed. And I don't care - I am DONE with dieting.
The sort of lies that are peddled on MN about "calories in - calories out" defy science (google 'overfeeding experiments' and follow the rabbit hole). The 'strain on the NHS' of someone who is obese is vastly overexaggerated and partly due to the undertreatment of conditions that doctors blithely assume are due to excess weight.
The true answer lies in taking the obsession and compulsion out of food - being able to use it as fuel and to be able to respond to hunger cues only - and being more accepting of all body shapes to allow people to do that.
When you don't think about food all the time, it gives your body a chance to sort itself out and begin to respond to hunger again - and I already see this happening in my own body. But what do diets do? They focus you on food, massively.
The diet industry persists in spite of how it fails - and because of how it fails. Everyone believes they just need to find the right diet, the one they can stick to. Well bingeing and starving worked for me for 40 years. Doesn't mean I recommend it.
I'm probably healthier now than I was then - but because I don't look it, then the likes of so many MNers will be making judgments of me. Well I judge them just as harshly - for the lack of empathy it takes to judge others on their size, and for the smugness of believing that being a specific weight bestows them with some form of moral superiority. Rather than indicating a lucky genetics and/or upbringing that didn't instill food obsession
The common-or-garden eating disorder is on full display regularly on MN, with the competitive under-eating of the mumsnet chicken, and the ma-hoos-ive salads.
Because who can even say what a 'healthy weight' is? I look like a ball too, but I'm fit as a flea again. The science that says a certain weight is 'healthy' is seriously flawed - so losing sight of what is a healthy weight, is like losing sight of a unicorn. You only lost sight of an illusion.
If anyone wants other places to start googling, they can try the 'Maintenence Phase' podcast.