To ask why it is that it is accepted that people can be naturally thin, but not naturally fat?

[MrsShawnHatosy]

Just that really. It seems to me that if one can be true so can the other. But fat is seen as something blameworthy, always.

“Naturally” in this context means the weight you are if you are not making much of a concerted effort around your overall intake, so naturally thin means thin without consciously restricting what you eat.

It’s the same with being naturally fat.

There's this study from the Lancet on women without any known metabolic conditions:

pubmed.ncbi.nlm.nih.gov/48002/

. 1975 Apr 5;1(7910):773-5.
doi: 10.1016/s0140-6736(75)92437-x.
Resistance to slimming: adaptation or illusion?
D S Miller, S Parsonage
PMID: 48002

DOI: 10.1016/s0140-6736(75)92437-x
Abstract
Twenty-nine women who claimed that they could not lose weight on prescribed diets were isolated in a country house and fed 1500 kcal. per day for 3 weeks. Nine women maintained weight within plus or minus 1 kg. and were characterised by low basal (B.M.R.) and daily metabolic rates and by a long previous history of dieting. The remaining women did lose weight, but there was much individual variation. B.M.R. is a good indicator of probable weight loss as a result of dieting. In the group as a whole it was more closely related to body fat than to lean body mass. It was also related to fat-cell number as determined by biopsy, but not to fat-cell size. These findings suggest that among a group of would-be slimmers who claim to be unable to lose weight there will be some who have become metabolically adapted to a low-energy diet and others whose inability to lose weight is illusory.
PubMed Disclaimer

I've yet to find any similar studies on people with a known gene or condition (these would almost certainly show massive weight gain in some subjects on 1500 kcal/day within a matter of days and weight loss on that amount would be incredibly rare). The fact that people with such genes or conditions haven't been subject to such academic research is probably partly due to ethics (diets involving reduced intake are known to damage metabolic health further therefore it would be unethical to subject those who already live with significant metabolic slowing to further restriction or, conversely, to put them in a situation that might cause enormous irreversible weight gain on an intake much higher than their daily limit) and partly because those who work with these groups are generally well aware that they would gain rather than lose on 1500 kcal/day - it's not under any sort of dispute. Although I've met endocrinologists who have (rather astonishingly) seemed genuinely unaware of the degree of restriction required with some genes or conditions, so such research would hypothetically be useful if there was a way to do it ethically. I do believe that there are a great many people probably living with undiagnosed medical conditions.

A very overweight pregnant woman though - not all people gain that kind of weight in pregnancy if that theory is true.

You're right that hyperphagia (overwhelming hunger and an intense drive to eat) is a key symptom of PWS and many other conditions associated with extreme weight gain and obesity but it seems pretty clear from the many, consistent reports from parents and caregivers of people living with these conditions that the obesity develops even when calories are severely restricted (i.e. highly restrictive diets do not prevent the extreme weight gain - they merely curb it).

People living with these conditions who manage their own diets will sadly always be open to accusations of dishonesty or mistakes with calorie counting but it's harder to discredit the people caring for them, who are not always relatives and who have often received training in how to weigh and measure every portion and avoid all the common calorie counting mistakes. These carers, whether family or not, are generally very committed to protecting their patient or child/adult child's health and also do not have the same hypothetical incentives to lie - why overfeed then say you didn't when you could just feed them the amount the doctor said they should get in the first place? Some are honest that their kids sometimes manage to sneak food from friends and neighbours but others live in remote areas and/or have kids with such extensive disabilities that they are able to ensure that this never happens. And yet, unlike their usually normal-weight siblings, the kids with the conditions that cause obesity are, funnily enough, still obese. These conditions simply wouldn't be so strongly associated with obesity if the obesity could simply be prevented with a sensible diet. It usually cannot be.

It's also clear that the charities and organisations supporting people with these conditions very much believe these reports, and why wouldn't they, when they're numerous and both consistent with each other and with what we know about the conditions under which animals become extremely resistant to weight loss? As I said before, you can make animals obese without overfeeding them in all sorts of ways - for example injecting insulin, damaging the hypothalamus or thyroid or breeding them to have the "wrong" genes - rats bred to have these wrong genes have more excess body fat on them after dying of starvation than rats with the "right" genes when living normal lives and eating to their hearts content - if death by starvation still hasn't made you as slim as your genetically blessed peers who are eating as much as they like, it's hard to believe that any diet would give you a better result!

Having personally read a great many blogs, articles and forum posts and talked directly with people who either have these conditions or are carers for them, I do not struggle to believe that many people live on under 1000 calories a day but are nevertheless still obese and often extremely so.

This why the discovery of ghrelin in 1999 was such a breakthrough (and, later, related 'messenger' hormones). A body knowing what food it needs is dependent on the continuously correct functioning of these hormone/peptide chains.

https://en.wikipedia.org/wiki/Ghrelin

That functioning can be disrupted by many other hormone-related conditions, and can also be disrupted from birth due to differing genetic profiles.

Other circumstances in the glorious variety of human biochemistry affect the in/efficiency of metabolism, metabolic heat generation, in/ability to digest or utilise essential nutrients, ability to create muscle instead of fat or vice versa, and interoception.

Regarding the charities and organisations that support people with conditions associated with weight loss resistance, here are some excerpts

From an American PWS charity newsletter

https://www.pws.org.nz/wp-content/uploads/2018/09/Beyond-the-Diet-For-the-Dietician.pdf

BEYOND THE DIET – For The Dietician By Janalee Heinemann - Prader-Willi Syndrome Association (USA)

"How many calories does it take for this child gain weight? Many dieticians put the child on a regular diet of 1,500 calories and then think that the parents are not being honest when their child continues to gain weight. It is not unusual to have to put a child or an adult with PWS on as low as 800 calories a day."

And from the Rawood Foundation that supports people with hypothalamic obesity, often caused by cancer or brain surgery:

https://www.rawoodfoundation.org/hypothalamic-obesity. (Raymond A Wood Foundation - "Working to Improve the Quality of Life for Brain Tumor Survivors:)

Imagine being hungry…really hungry…all of the time and nothing satisfies that hunger.

Imagine eating less than 900 calories a day, yet you are still gaining weight.

Imagine the struggle you face with your family and caregivers who are locking up cabinets and refrigerators to keep you from eating everything in the house.

Imagine mom and dad finding you eating out of the trash can.

Imagine experiencing this because you survived a brain tumor.

This is hypothalamic obesity.

There's also this interesting article about a woman with Cushings (where extreme weight gain is caused by a brain tumour)- https://www.dailymail.co.uk/health/article-2510680/32st-woman-lose-weight-diagnosed-hidden-TUMOUR.html

This 32 stone woman claimed to be eating only 800 calories a day and was clearly not believed until she ended up in hospital for 8 months over something unrelated. It's implied that staff only realised she was telling the truth when they were able to monitor or perhaps even control her food intake around the clock and saw with their own eyes that she remained massively overweight even when eating relatively little.

It's somewhat true and I say that as a naturally slim person, but the difference is that for say obese people most will have been slim in the past and then had to overeat to get to that point.
After that their weight set point tends to be stuck and yes plenty can lose weight but it won't stay off because their weight is naturally set at a higher weight set point.

I do think there should be more education on this, people think that weight gain is reversible but it often isn't. Yes I know that these days there are weight loss injections but aside from those it can be very difficult for people to reverse it. I believe prior to weight loss injections it was only 1% or less of obese people managed to get back to a normal weight, and keep it off for at least a year.

I know some don't believe in weight set point theory, but I know from my own experience that mine is ridiculously rigid as a slim person.

I'm naturally slim/thin, whatever is the correct terminology, as are my parents and sibling. I do have a little belly now, because I eat too much, but if I didn't have the metabolism that I have I would definitely be more overweight, as I most certainly eat more than I need.

I never put weight on anywhere other than my belly though, and that's relatively limited. I do think that's there is more to it than purely the quantities that one eats, there is an element of 'natural' bodily ability to process calorie intake.

Actually, there was a programme on the BBC back in 2008/2009 called Why are Thin People Not Fat? It pointed out that much of obesity research is focused on the overweight and the assumption that they are all eating too much while nobody is actually studying thin people and whether their thinness is actually caused by sensible eating. It was fascinating. They all ate what I'd consider to be a massive amount to begin with and had to up their calorie intake to something crazy - like 5000 or 6000 calories a day for the actual experiment iirc (just looked it up and it seems they had to double their intake so it would have been a different amount for each). They were practically pouring melted ice cream down their throats and eating entire blocks of butter (ok, maybe slight exaggeration, but not much) and it was absolutely astonishing how little weight they gained. Some gained only a few pounds over the entire experiment and all lost it quickly and easily with virtually no effort at all when they went back to their normal intakes. Now compare that to someone with a disorder like Cushings or PWS who could probably gain a similar amount in a few days if they went anywhere near 1000 calories and the difference is insane. I think it's obvious that some thin people eat vastly more than some overweight people even if that's obviously not always the case.

This simply isn’t true. I have photos of both my Great Grandmother and Grandmother during both world wars.Neither can be described as anything less than overweight incredibly round women. Fat feet, big thighs, large hips and stomach with big breasts. War time and rations didn’t change this at all.

Further to this all of the family in the generations after have had exactly the same shape and despite diets and exercise we have all stayed on the larger round body frame size. So much so that the only reason I ever doubted my sisters parentage was because she was stick thin shaped, and I was indeed correct in my thinking later finding out she was adopted.

That's so interesting! Can I ask what kind of lives they lead? Did they work outside the home? Have loads of kids? Were they from affluent or low income families of origin? Were their husbands high, low or middle earners? You don't have to answer if I'm being too nosy - these things just fascinate me!

My Great Grandmother had 5. She worked way into her old age and her husband died in the First World War leaving her a widow at 34. I think they were quite middle class. She actually lived with my father and my Grandmother. My Grandmother was a seamstress and worked very hard in theatres making costumes. Neither drove so walked everywhere and got the bus rarely. My Grandmother was slightly well off affording for her children to go to private school because of my Grandfathers job in the Second World War. Despite this my dad would still talk of rations and neither his Gran or mum were good at cooking so their diet was average for back then. My dad was a “well built” man too, although never eating anything processed, his greatest claim was only having one McDonald’s in his entire life and even then he didn’t finish it , he worked and cycled daily way into his 60’s. He didn’t end up as well off as his background and was a manual worker living in social housing. My Great Grandmother died at 97, my Grandmother at 50 but that was due to blood poisoning and my Dad at 81. My aunts are still going into their 80’s and I have an uncle of 92. No heart disease or cancers in the family either. Touch wood.

When people talk about "severe calorie restriction", that's usually relative to the average person, not necessarily relative to what that individual's body actually needs.

I also don't think blogs, forums and personal accounts are strong evidence. Carers are usually doing their absolute best, but when someone is constantly distressed by hunger it's understandable that intake isn't always measured as perfectly as people think. That's why controlled studies are more useful than anecdotes, and I haven't been able to find any controlled study which shows people remaining extremely obese while on under 1000kcal diet long term. In fact I've found research that proves the opposite, that obese people who are put on carefully monitored, very low kcal diets lose weight.

I tried researching the animal studies you mentioned, but from what I've seen, the studies show you can make animals predisposed to obesity by increasing appetite or reducing energy expenditure. They don't show animals becoming obese regardless of energy intake and output.

Ultimately, my point isn't that some people are more prone to obesity than others - they clearly are. My opinion is that people cannot remain obese despite consuming less energy than their body requires. I haven't seen any evidence contradicting this.

I can believe that. My husband is 6’4 and weighed 9 stones while very poorly in hospital. They told him he could be discharged when he hit 12 and a half stones. They put him on a high calorie diet to build him up. Lots of full fat and sugar. The weight literally crept on. A few weeks later he’d only put a stone on and they changed him to a normal diet because they were worried about his heart/arteries and discharged him at 10.5 stones. 27 years later he still hasn’t hit the target of 12.7 stones! (He has had several more major bowel operations and now has a stoma, and he doesn’t enjoy food in the sense that I do, I think eating has caused him so much trouble over the years..). But I would definitely say he’s a naturally slim, even thin, person. A bit like when I had a thoroughbred horse it was really difficult to keep up to weight, whereas a cob type horse is hard to keep slim. Both may be the same height, although the cob would have a much bigger frame and would weigh more if they were both slim.

I think our idea of “fat” is now massively skewed in the UK. What once was considered fat, is now considered normal. So 12-14 or 14-16 even can be “naturally fat”, but now we just see it as a normal build.
People getting into the 16+ bracket are probably overeating and not exercising enough. Then again, height differences and so on.

BMI always seems like a crap measure to me. My friend is technically overweight, but runs marathons. She’s just short and very curvy and BMI doesn’t seem to account for that. I’m always fairly slim, about 18 BMI, but eat crap and couldn’t run a mile. It’s very clear which one of us is healthier, and you can see just by looking at us.

We should probably stop worrying about what shape is “natural” or not, and all just try to eat less shit and walk more.

Totally agree OP. And I speak as one "naturally thin," when I KNOW I don't particularly have to try. I think the rise of semaglutide makes it very clear that there is a lot more to being overweight than some moral failure. I also think the fact that a lot of psychiatric drugs (and other medications) cause weight gain again illustrates the point: weight is not purely a matter of what you decide to eat, or even of what you eat. Some people don't need antidepressants or antipsychotics but that doesn't imply they're so virtuous, they're just lucky; their bodies naturally produce the right chemicals perhaps. Some people are "naturally" slim. (Maybe their bodies naturally produce some form of semaglutide?) Lucky them, but it's not a sign they're more virtuous or clever than everyone else.

When people talk about "severe calorie restriction", that's usually relative to the average person, not necessarily relative to what that individual's body actually needs.

I can't say I've noticed this at all - I hear it used much more commonly to refer to the latter but I think we probably spend our time talking to very different groups of people.

I also don't think blogs, forums and personal accounts are strong evidence.

I disagree. With so many examples of the medical orthodoxy of one era ending up so thoroughly discredited by the next, I think we must always make a point of listening to what the people who are actually living with these issues are telling us about their lives (they're known as the real experts for good reason). Especially when these accounts are consistent with each other and with existing research on metabolic rates, both in the general population and in those with metabolic abnormalities. More on that later.

Look at the enormous harm that was done when doctors and scientists decided that ME/CFS was a psychosomatic condition and could be successfully treated with Graded Exercise Therapy, supposedly on the basis of solid scientific research, but against everything their patients were telling them and the world about how they experienced their illness. Both directly but also through blog posts, forums and personal accounts. For years these patients were written off as unreliable witnesses to their own lives and bodies because their reported experiences contradicted the erroneous medical orthodoxy of the time, while great harm was done to them, physically and pschologically. The tide eventually turned and the approach was discredited but it took taking patient/carer testimony seriously to achieve this outcome and improve scientific standards and rigour.

Something similar has happened to a lesser degree with exercise. It's beginning to look like the medical establishment has been wrong all along - that it doesn't induce weight loss for the majority, even with a calorie controlled diet. Millions of "anecdotes", in the form of blogs, forum posts and personal accounts have been telling us exactly this for decades but we chose not to listen, or else we gaslit people into thinking they were accidentally overeating in response, to explain their lack of results. Again because they contradicted the orthodoxy of the time. We must surely learn from past mistakes.

Carers are usually doing their absolute best, but when someone is constantly distressed by hunger it's understandable that intake isn't always measured as perfectly as people think.

I think we need to resist the temptation to write off all of these people as being unreliable reporters just because some of them will be. Yes, of course, with PWS in particular, food sneaking happens a great deal (as strongly evidenced by forums and blog posts!) and of course some carers will sometimes succumb to the pressure when faced with a distressed child or adult, but with 350,000 to 400,000 people worldwide living with PWS alone, I don't think it makes sense to decide that nobody in the history of the condition, or any similar condition, could ever have managed to keep their child or patient on the strict diet they were prescribed. At least for a month or two which is all that would be needed in practice (although I don't struggle to believe those that report that they can maintain these diets long term). Ultimately, common sense suggests that some percentage will be in a position to achieve the strict level of adherence required, especially given that some parents and carers are scientists, doctors and nutritionists by training and because, as noted before, some patients are non-mobile, non-verbal etc so the carer has more control.

I'll split this up as it's getting too big...

continued....

That's why controlled studies are more useful than anecdotes, and I haven't been able to find any controlled study which shows people remaining extremely obese while on under 1000kcal diet long term.

There are no long term studies of caloric restriction done under controlled conditions as far as I'm aware - it would be prohibitively expensive and logistically impossible - people have lives and cannot live under lab conditions for any significant amount of time even if it could be funded. All such studies are therefore small scale and short term. It's also unethical to put people with compromised metabolisms on VLCDs (lower than what they're already eating) as it can reduce/damage their metabolism further. And those already eating less than this obviously wouldn't sign up as they'd gain weight. However, I would point out that this can be proven in other ways if you buy into calorie science (and while I'm a sceptic, it sounds like you do).

• Studies of adults with no known metabolic abnormalities have found RMR/REEs below 1000 kcal/day, eg Mifflin et al and Pavlidou et al, found REE/RMRs as low as 927 kcal (REE) and 908 kcal (RMR) respectively in their relatively small samples. Implying maintenance diets of 1089 and 1112.4 kcal/day, assuming the relatively sedentary lifestyle this metabolic rate would likely imply, (TDEE is typically estimated at 1.2 times RMR/REE for sedentary lifestyles). Not much, if anything, would be lost on a diet of 1000 calories a day for these cases. While these results were the lowest in the samples, a statistical analysis of these studies provided by exercise physiologist Greg Nuckols at https://macrofactor.com/range-of-bmrs/ suggests they aren't hugely out of line with the norm and that around 1 in 5 women has an RMR below 1200 kcal/day (or possibly even 1 in 5 people - his wording on that is a little unclear). While Greg Nuckols seems to be appropriately qualified, I don't know that much about him and haven't studied statistics beyond first year uni level (many years ago) so maybe someone will come along and dispute his work, but it does fit with what the blogs and forum posts of people struggling with their weight say about their intake so it rings true for me.

• It has been shown (from controlled experiments again using indirect calorimetry) that people with PWS have RMRs/BMRS that are on average 30-40% lower than the general population (I think I've read studies that find an even larger difference but this will do for now). Those reporting that their minor or adult child (or charge) with PWS eats 700-900 calories a day to avoid gaining (or gaining excessively) are reporting more or less exactly what this research suggests would be their maintenance intake given the lower end of the scale for people with normal metabolisms.

• All of this is consistent with the fact that the lowest recorded resting metabolic rates are below 600 calories a day. The lowest recorded RMR/BMR that I could quickly and easily find was 595 kcal/day (https://pmc.ncbi.nlm.nih.gov/articles/PMC3458581/), meaning a weight maintenance diet for this person would be around 714 kcal/day (again, it's hard to envisage anything other than a relatively sedentary lifestyle when your metabolism is so low). Such a person would gain weight rather than lose it on 1000 kcal a day. The lowest recorded RMR I could quickly find in an obese person (apparently without metabolic abnormalities) was 658 kcal/day (https://pmc.ncbi.nlm.nih.gov/articles/PMC11365691/) suggesting a maintenance diet of around 790 kcal/day is - again this person would also gain rather than lose on 1000 calories a day. At least if you believe that eating above your maintenance rate causes weight gain and below it weight loss.

As a final note on this point I will mention the case of Naomic Benton, who had Cushings. This might be as close as you'll get to a long term medically observed failure to lose weight on a low calorie diet (I presume her ward had control over her intake and that facts were checked with the hospital where she was treated). When her Cushings tumour was found and removed it's reported she managed to lose the weight quite easily proving her obesity was never caused by overeating to begin with and couldn't be solved with diet or exercise.

Continued

I tried researching the animal studies you mentioned, but from what I've seen, the studies show you can make animals predisposed to obesity by increasing appetite or reducing energy expenditure. They don't show animals becoming obese regardless of energy intake and output.

I don't think I mentioned any specific studies and there are thousands of them so I don't know what you've read. You're correct that obesity isn't independent of intake and output. But that's not the same thing as saying that weight loss can always be achieved by eating less, moving more or some combination of the two or that it's not possible to be overweight on a level of food intake not adequate to meet nutritional needs. People see these as being one and the same thing but they're not. Gary Taubes' award winning books explain this well (even if his theories on carbohydrates haven't so far been validated).

Ultimately, my point isn't that some people are more prone to obesity than others - they clearly are. My opinion is that people cannot remain obese despite consuming less energy than their body requires. I haven't seen any evidence contradicting this.

I think the piece of the puzzle you're missing here is metabolic adaptation. And you're also assuming that the body will always start burning fat as soon as it's not getting enough energy for optimal functioning which I don't think is true.

If someone is obese but their weight is steady on 1500 calories a day, for example, you might argue that reducing intake by 500 calories a day will bring about weight loss. But there are two ways the body can respond to such caloric reduction which shows why it often doesn't (and both are outside an individual's control).

The first is to keep the metabolic rate steady (1500 kcal/day) and to burn body fat to replace the calorie deficit from food (so the person burns 1000 calories from food and 500 calories from body fat). The second is to reduce the metabolic rate more or less immediately in order to defend body fat reserves - this means that while yesterday you were burning 1500 kcal a day, today on the new diet you've switched to only burning 1000. You're eating vastly less but your body's response has wiped out the deficit you were trying to create, although you might notice you're now exhausted by daily activities that previously you could manage (the body is getting less than it needs for optimal functioning but not less than it needs for survival).

People whose bodies respond in the first way will lose weight on diets. People whose bodies respond in the second way will not (this is probably what is happening is this research paper detailing a group of women in which some lose weight when put on a diet and some don't) . Exercise, as mainstream scientists are finally acknowledging, will make no difference to most. Resting metabolic rate simply slows down to compensate for the increase in metabolic rate during the period(s) of high activity and any advantage is wiped out by this mechanism.

While some people will be in either the first group or the second group their whole lives, a great many people will start off in the first group while young but end up in the second group as metabolic dysfunction takes hold. If I remember correctly, this was more or less the conclusion of Gary Taubes book Why Do We Get Fat? While weight loss science is phenomenally complex in some ways, most people ultimately end up overweight because, over time and due to metabolic adaptation, we simply lose the ability to lose weight. Although maybe the new generation of weight loss meds will turn things around for some of us?

The women you mentioned are thin, not slim

In my teens/early twenties I was slim and lived on fags, alcopops and pot noodles with the occasional bowl of sugary cereal thrown in.
I put on a small amount of weight in my thirties (size 12) when I started to eat more normally. As I’ve got older (forties) my legs and hips have gotten bigger and I have a stomach now. (Size 14) I eat around 1500 calories a day, go to the gym twice a week and do Pilates, yoga and swimming. I have been diagnosed with lipodema in my legs and hips which means the fat stores don’t respond to normal weight loss techniques. I can’t seem to lose any weight.

But they weren’t too thin when they were younger, they were slim. Now KM ma have lost weight due to pregnancies and illness, but VB is definitely thin due to not eating. (I’ve had her as a passenger on a flight when I was long haul cabin crew and she didn’t eat anything for the whole flight. Very common with celebrities famous for their looks. Even men).