The official figures for "spontaneous hypothyroidism" is 2% of the U.K. Population. So that's 1.5mn right there, but then a leading world expert in the Field is highly critical of how its Dx & treated in U.K. And believes 20% is a more realistic likely stat. That would be 13mn people. In USA and Australia (similar genetic make up to uk) figures are nearer to 15% and there will be people in those countries also undx so I think his 20% is probably accurate.
B12 deficiency - even the nhs acknowledges that this affects around 10% of the population. That's 6.5 mn people
Around 5% of Brits are on corticosteroids for asthma, struggling to find stats for use for other conditions.
4mn Brits are long term on antidepressants most of them slow metabolism/increase appetite/artificially lower blood sugar. No stats for shorter term use.
Steroids and antidepressants are the most commonly prescribed drugs that are known to affect weight. There are others.
Mobility - again a difficult one to get stats for as several disabilities/conditions can cause this but 1.2 mn Brits are regular wheelchair users. There's 11 mn Brits are registered disabled but that will include disabilities that don't directly affect mobility.
Then I get into really tricky territory statistically as there's certain SN conditions which can affect metabolism/appetite/the persons ability to control their intake but even knowing how many people have those conditions won't inform how many are affected that way.
Then there's addicts - many addicts switch substance addiction for food addiction. Even "milder" addictions, I certainly know plenty of smokers that swapped the fags for sweets.
All figures are either nhs, ons or national charities specialising in certain conditions mentioned. So I think fairly reliable sources.
The ones from outside uk are their govts stats.
So I really don't think it's a stretch to consider that yes many of those overweight have an underlying condition that's at least making it harder than it would be for someone else to lose weight.
I knew a couple of people who for YEARS were very proud of their slim "status" and being able to eat what they wanted - turned out one had hyperthyroidism, the other had another metabolic disorder with same effect of vastly increasing metabolism.
Noeffingidea - when I was a nurse I was slim and some others were slim, but I certainly noticed a fair amount of overweight nurses (and other hcps) even then (90's) But I was younger and pre-pregnancy then. Yes missing meals may contribute to slim-ness IF you're not then starving later when you do finally get to eat and so succumb to high cal fast food. When I was nursing the canteen in my hospital was excellent - filling hearty but healthy food and open 24hrs. From speaking to friends/ex colleagues now many hospitals have done away with staff canteens altogether, they're certainly not open 24 hrs and it's more junk food, it's that or vending machine crap or somehow find the time & energy to make something cold to bring in - but nothing that needs either refrigerated or heated as neither facility is generally available. Personally I think such measures are a false economy. Staff are usually happy to cover the costs of such a service when it's good and staff that are well fed will work more efficiently and it boosts morale too.
Satsuma eater - I used to live in Netherlands and I agree a decent cycling network in uk would work wonders for increasing people's exercise/activity levels. Govt tends to forget most jobs now are physically sedentary but mentally exhausting so people aren't active at work and are generally too knackered to exercise outside work. I've also lived in uk cities with good cycling networks and the local population was generally slimmer. Easy to hire bikes/bike sharing schemes also help.
Yes we ate differently in the past but looking to my grandmothers and even to an extent my mother they were more active in walking to work (many peoples workplaces now are too far to walk to), doing manual or at least standing jobs (my mother is forever saying how checkout staff have it cushy now as they get to sit down! And when the till isn't busy they're not deployed elsewhere shelf stacking or pricing up) plus the chores! One of my grans still had a twin tub, Manual wringer and scrubbing board until I was in my teens! She also believed scrubbing floors on hands and knees and beating rugs worked better than mopping and hoovering.
Mum would still handwash if there wasn't enough for a full load. Most of us now either avoid buying hand wash only items like the plague, put them in the dry cleaners or risk the "handwash" cycle on the automatic machine and pray
I'll probably get flamed by certain posters but I think cost is a factor too. I'm in Scotland and many councils up here fund free swims for school age DC and pensioners (sadly starting to go due to the cuts) and from the research I've seen this apparently did make a difference to obesity levels in the areas it was/is operating. In some areas there's also outdoor free gyms (often next to play parks so the kids can be running around playing in the park and mum/dad/whoever can workout while keeping an eye and council run walking groups - again in these areas the obesity levels seem to be lower.