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AIBU?

Share your dilemmas and get honest opinions from other Mumsnetters.

Sister is 55 and suddenly obsessed with her weight

100 replies

youlookradishing · 14/05/2026 10:41

She’s always been ‘normal’ weight, typical 5ft 5 size 10-12. She’s been happily married for over 30 years and has had 3 children, just for context.

We used to have normal conversations about a range of interesting stuff. She’s always been a bit rigid and moralistic about things, but it’s just her personality.

Over the past 2 years or so though she’s become obsessed with her weight and being slim. Most conversations will include comments about how X or Y food isn’t good for you or how she eats 30 different grains a day or whatever. She’s not bothered about her ‘looks’ per se, she never wears makeup and doesn’t spend much on clothes, but she’s now a very slim size 8. She tries to persuade me that if we have a ‘big breakfast’ (by which she means several slices of toast and a piece of fruit) then we won’t ‘need’ lunch. If we go out for a meal she will have a salad without fail and she runs 5k every morning. She says this is all about being healthy, but she is always weighing herself on the fat / bmi machines in Boots. Her bmi is now about 18.5 so verging on underweight.

She casts judgement on others and seems to be using this as a way of making herself feel good in comparison. She’ll tell me that a certain celebrity now looks “awful” and when I google them they actually look fine, they just got older and put on some weight. Or comment to me about how a certain friend “eats doughnuts” as though it’s something she expects me to be aghast about.

Anyway I’m not sure what I’m asking here: I’m a bit nonplussed because I recognise some this attitude from my teens in the early 00s when sneering at ‘fat people’ was unfortunately more of a mainstream attitude and being double size zero was held up as a virtue.

But she’s 55 years old! This seems to have come from nowhere as she had a normal attitude about weight until now (or so I assume). She grew up in the 80s which I know were an unhealthy era for body image, but that was a long time ago now and there is more body size acceptance today than ever before!

I suppose I’m asking anyone if they recognise this pattern of behaviour? Could it be menopause related? She’s also just taken early retirement (at the same time as her husband, who is 60), is she having an identity crisis?!

(I do know the obvious answer is to speak to her, but I don’t see her that often, we are not v close in age and live some distance apart, in the meantime I’m just interested to know what you think and whether you’ve known this happen to anyone in your lives?)

OP posts:
ShetlandishMum · 14/05/2026 10:44

Whatever floats her boat. Wouldn't think a lot about it.

BelleDeJourRose · 14/05/2026 10:45

Yes, I'd think it's linked to the early retirement given its happened at the same time

CupcakeDreams · 14/05/2026 10:46

Maybe she just understands that if you gain weight and get older, it's a recipe for inflammation and immobility. People who are new to this, after not being bothered or having just learned, can be fixated and try to tell everyone else about it, too. They like to share their new found passion and knowledge as a way to help others and maybe have someone to go through the journey with at the same time. Doesn't sound unhealthy to me. More people should be interested in their health as they get older and not just giving in to age.

BelleDeJourRose · 14/05/2026 10:47

Oh just seen it started 2 years ago, so maybe not

BelleDeJourRose · 14/05/2026 10:49

I guess if she starts to lose even more weight and gets too thin, it would be worrying.

rivalsbinge · 14/05/2026 10:50

Could be identity, menopause all kinds of things are you worried about a ED? Has any other part of her personality changed?

As a close friend I’d said “are you ok” so I assume as her sister you could raise this and ask her what’s happened or changed and is she feeling OK.

Or she could just be in her fitness phase? I went though one of theses 8 years of weightlifting and training became a huge part of my identity I must have been a bore and I cringe at the fact I took my Tupperware prep to meetings and client events to avoid the sarnie spreads.

I will say is a never mean about other peoples weight or eating habits, I was very focused on my own path.

PennySweeet · 14/05/2026 10:51

If you don't see her that often I wouldn't pay it too much mind.

If she decides for both of you that you won't need lunch, tell her you'll be having yours.

youlookradishing · 14/05/2026 10:51

BelleDeJourRose · 14/05/2026 10:47

Oh just seen it started 2 years ago, so maybe not

It’s been a slow build up really, the running started 2 years ago. I see her about 4 times a year so it’s taken a while for me to take it seriously.

OP posts:
youlookradishing · 14/05/2026 10:53

I guess I am worried about it being disordered in some way, even if not a full blown eating disorder.

But I guess I also just want to understand. Last time my behaviour was anything like hers I was an insecure teen who wanted boys to fancy me and girls not to bitch about me. I struggle to see where it’s coming from with her.

OP posts:
MustardGlass · 14/05/2026 10:55

It’s sounds like she is trying really hard to stay healthy as she ages.

Orangesandlemons77 · 14/05/2026 11:04

She ought to be careful with the risk of osteoperosis at low body weights. Maybe you could mention it to her? She might need e.g. a DEXA scan

CupcakeDreams · 14/05/2026 11:05

youlookradishing · 14/05/2026 10:53

I guess I am worried about it being disordered in some way, even if not a full blown eating disorder.

But I guess I also just want to understand. Last time my behaviour was anything like hers I was an insecure teen who wanted boys to fancy me and girls not to bitch about me. I struggle to see where it’s coming from with her.

Edited

Healthy living and exercising can become a pretty time consuming hobby. Lifting and running releases endorphins and taking care of ones self builds self esteem. I think it sounds great for her.

BridgetJonesV2 · 14/05/2026 11:08

Sounds like very disordered eating, and I'd be a bit worried about her. Especially if she's skipping meals and running. My son in law has started running 10k a few times a week, and the amount of food he eats to fuel up for a run is unreal. If she's depriving herself of food and exercising, there's going to be an issue with her health at some point.

Can you try and talk in private to her husband about it? Ask if he's noticed anything or if he's worried too?

BauhausOfEliott · 14/05/2026 11:11

youlookradishing · 14/05/2026 10:53

I guess I am worried about it being disordered in some way, even if not a full blown eating disorder.

But I guess I also just want to understand. Last time my behaviour was anything like hers I was an insecure teen who wanted boys to fancy me and girls not to bitch about me. I struggle to see where it’s coming from with her.

Edited

I struggle to see where it’s coming from with her

You don't need to see where it's coming from. I think she probably is obsessive and probably has a low-level eating disorder, but she obviously isn't going to accept you telling her that and ultimately although her BMI is low it doesn't sound like it's dangerously low, so I think you just need to let her get on with it.

You can, however, tell her that you don't want to talk about food / weight with her or listen to her judging other people if you - quite understandably - find that uncomfortable or excessive (because it sounds like that's the real issue for you, rather than her actual eating habits).

HoldMyWine · 14/05/2026 11:13

I am the same age as your sister and for some reason women my age are being bombarded with information about what we should eat (more protein!) how we should exercise ( lift heavy!) what supplements we need to take ( creatine!) how we should age naturally but still be wrinkle free. It’s relentless and hard not to be swept along with it all.

fivepastmidnight · 14/05/2026 11:13

If she's retired, she may just have become more aware and focused on her own mortality and the need to be healthy but expressing this in a judgy way.

OriginalSkang · 14/05/2026 11:15

It sounds like she's thinking a lot about healthy eating rather than about her weight?

NoctuaAthene · 14/05/2026 11:17

Yes I think it likely is linked to getting older, retirement, menopause - all quite scary big life changes and can lead to a lot of feelings and fears about your identity and value to society, purpose of life etc. And one very common reaction to such feelings is to try and impose a sense of order and control over your life, e.g. in the case of fears about health and/or appearance by dieting or exercise. Sometimes this can be quite positive motivation but it can also lead to defensiveness and criticism/ blaming others that make different choices - it's all about control and psychological security, the (sub-conscious) thought process goes 'I don't want people to think I'm ugly/get weak and sick, if I eat salads/go to the gym that won't happen, Julie eats donuts / sits on the sofa, therefore people will think she's ugly/she'll be a frail old person, Julie is wrong and I'm right'. Obviously it's illogical because we all can think of plenty of examples of chain-smoking couch potatos who lived to 90 and whippet thin gym bunnies who sadly get ill and die young, obviously it's not the direct causal link your brain would like, plus the things we fear most - ageing, getting sick and dependent on others, other people's perceptions of us changing - are sadly pretty inevitable, maybe you can change your risk factors in either direction slightly or improve your experience by your choices but the grave comes for us all in the end no matter how much we stick our fingers in our ears and say la la la.

I think if you feel able to, doing some gentle disruption of this pattern of thinking, doesn't have to be a big confrontation but a little joke or a 'I think Sarah looks great, she definitely doesn't need to lose weight, why would you think she does?' or 'I actually really do like donuts too so I'd appreciate you shutting it with the criticism of Julie' or however you would naturally interact with her - she likely won't completely change but may give her pause for thought. And just model a healthy attitude generally of enjoying your food in balance, but otherwise try and just be tolerant and understand it's likely all coming from a place of insecurity in herself?

Bristolandlazy · 14/05/2026 11:18

I imagine it's linked to her mortality, it gets more real the older you get. Good for her but it sounds like she's a little obsessive and boring company at times.

bigboykitty · 14/05/2026 11:18

It sounds like orthorexia to me, OP. I'd be concerned too. It sounds like it's taking over her whole identity. I'm guessing it might be filling the space that used to be taken up by her work. Have you mentioned what you've noticed to her?

PennySweeet · 14/05/2026 11:22

CupcakeDreams · 14/05/2026 11:05

Healthy living and exercising can become a pretty time consuming hobby. Lifting and running releases endorphins and taking care of ones self builds self esteem. I think it sounds great for her.

I agree.

It sounds like she's become a bit of a bore with it, but then some people do when they get into something new.

I think the OP is overthinking it.

outerspacepotato · 14/05/2026 11:28

She's taking her health seriously and has stepped up her game. Unfortunately, she's become evangelical about it.

Change the subject. Tell her you don't enjoy her talking about other people's size or what they eat.

Charlotte120221 · 14/05/2026 11:29

I'm that age and second the poster who said we get bombarded with health supplement and weight loss jab ads.

I also think that our age, the kids have left home, we're moving towards the end of our careers, we're wondering what's it all about? My running definitely plays a far bigger role in my life than it used to - it's expanded to fill the space. Maybe the eating/diet/exercise has done the same in her life and she's struggling to get perspective?

The eating thing does sound a little obsessive, but she's only just below the healthy range.

Pinribbons · 14/05/2026 11:32

I became much more interested in diet and weight when I started running.

I was never bothered about my weight just from a looks pov, but every pound lost (assuming not very underweight) saves about 2 seconds per mile, so half a stone over 5k is c. 45 seconds which is huge. My running is important to me so I fuel it and manage my weight accordingly, and yes sometimes I like to talk about it. It's a big part of my life.

I don't think I'm judgemental about others' eating (at least not out loud) but whenever I meet up with old friends who don't take their diet as seriously, it is shocking how old and unfit they appear, compared to my running friends. I think in your 30s and early 40s you might not notice such a difference, but by late 40s and definitely 50s, the people who haven't exercised and taken care of themselves may as well be a different generation.

MeridaBrave · 14/05/2026 11:36

I’d be saying that it’s not healthy to be obsessed about weight without considering muscle mass - and with BMI of 18.5 she is at risk of low muscle mass. I’d be encouraging her to do a dexa scan esp if the exercise is running rather than weight training.

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