My SIL is a competitive undereater and it's wearing me down

Hahaa. No I'm definitely in the call them out camp.

Nice time she mentions dress size say something like "yes Fiona you are still amazingly tiny ( she's insecure and needs positivity) . You don't eat much though and I've eaten loads . I just love the decadence.".

So she knows you are actively choosing to eat exactly what you do.

I suppose if you wanted to "get your own back" on her, you could do a whole faux concern thing every time she talked about being "stuffed" or her small dress size. So instead of it being a "good" or "enviable" thing to be underweight, it was called out for not being healthy. (I'm assuming you aren't concerned about her eating/size from your comments)

Each time she asks if you are going to finish your plateful, just enthusiastically agree, say that you are really going to enjoy it and give a big smile. Keep on doing that, show you don't share her hangups around food.

I hate this so much. People having a pop at the OP have obviously never been on the receiving end, although I think the comments about her looks were unnecessary, no need for armchair psychology.

I agree try to sit as far away from possible. Once a month is a lot!

I think I would go out of my way to eat as much as I could in front of her whilst giving her a hard Paddington Bear stare.
Her eating disorder is her business, your life and mental well being is yours. She can then like it or lump it.

I have the opposite in my wider family - people who eat loads and then keep commenting on the ones that don’t have the same large appetite, they competitive over eat. 😂
I agree it’s grating when people do things like this. I don’t know why people can’t just concentrate on what they are eating and enjoy it, rather than make other people feel bad about what they are eating.

Would drive me absolutely bonkers. My mil is like this. I didn't see her much during my pregnancy because I couldn't stand hearing the unwelcome comments about how enormous I was... I wasn't and haven't ever been fat but she makes me feel like I am!! 🤔

Really? - That was just plain nasty. Would you say the same to someone who was bipolar? Or had severe post-natal depression?

My mother is like this. I used to just ignore it then we had more young women in the family and it became a real concern to me that they would pick up on this.

So now I say things like ‘yes I’m lucky to have a good appetite’ and I say and do only positive things around food.

The best response is 'yep!' and just tuck in. Sod them 🤣

I work with some of these people, I make a point to eat more and enjoy my food around them. Especially as I'm a healthy weight and enjoy the looks of horror as I have a 2nd helping of pudding with extra cream 🤣 best way to shut them up is show them you do not care.

You’re always worried about portion size Sarah. My friend did Weight Watchers & learned a lot, you might find it helpful!

How bizarre. You'd think if someone was thin then it's obvious they are thinner than the others. What difference does it make if they order 3 courses plus cheese or just a salad? The person is the same size regardless?!
Does she think she'll suddenly double in size before your eyes on consumption of one calorie?
Just totally ignore any chat from her about food. It's a really weird way to be in public. I suffer from anorexia and would never behave in this way. If I don't want to eat much I just don't. I don't impose it on other people or talk about it at the table! She just sounds really rude tbh.

There isn't much you can do except try to ignore it. I'm sure you can't be the only person who has noticed. If it's a general comment aimed at whoever happens to be listening, don't engage. If it's directly aimed at you, just give a vague, noncommittal answer. If she tries to push for a response, change the subject/get up and go to the toilet/suddenly remember you left your phone in the car. I certainly wouldn't be trying to play her at her own game or playing any sort of game at all as a couple of pp's have suggested. There isn't anything much you can say out loud in front of others that wouldn't humiliate her. And personally, I wouldn't be going down that road if she is struggling with disordered eating.

So annoying and I would be tempted to point out how tiresome it is to her. Or just absolutely gluten myself at the next event whilst she looked on in horror. Underweight 40yo women turn into frail and wrinkly 60yo women.

My MIL does this to an extent so I do understand ‘oh I could never eat that much’ ‘I don’t eat very much you know’ ‘I used to weigh six stone I’m so big now’ ‘I don’t know any other ladies who drink beer!’. I just ignore it really and eat whatever I feel like as a principle.

Both my mil and sils are like this. It is extremely tiring and annoying. When I first met the three of them 20 odd years ago, they immediately pointed out how big I was (then a size 12) and how much food I could eat. Little did they know that I had suffered for years with an ED. They would literally eat some lettuce for lunch and then watch with horror as I tucked into meat, veg etc.

Now I am in my 50s I couldn't care less what they eat, what they think about my size or the comments they continue to make about my eating, although it bothered me terribly when I was younger. For the record, they are now all suffering with osteoporosis and look far older than their years.

I'd go the other way then, and make a massive thing about how much you eat, how life's too short to deny yourself. Really trowel it on.

This sounds like my sister and it got to the point after seeing how screwed up one of her children is about food that I reduced contact drastically so my daughters were not exposed. Her son sits there and says he can't eat that because he'll get fat and asks how many calories are in everything. My sister says it is due to a 'healthy eating' lesson they did at school.... 🙄 She says she's always told him it's her issue and not his to take on...

She was anorexic as a teenager but still she announces she won't be eating the family meal. She brings a little pot of granola to pick on but makes a massive show of it. She sapped all enjoyment out of a meal time and time and time again. I grasp that living with an eating disorder isn't fun, but bloody hell, at 45 years old do it quietly so that the children don't hear it all.

Never again.

Yeah it does sound tiresome. She probably won’t change so it’s just a case of working at not letting it bring the mood down, for you. Maybe even make sure you’re at the other end of the table or something.

Does she actually have an eating disorder?

If not, YABU for diagnosing her with one (it's quite possible to just be annoying about wanting to be the slimmest etc).

If so, still YABU for not having more sympathy because eating disorders are very serious things.

How many times do you eat with her anyway over the course of a year? If she's getting to you this much, cut down on eating together.

This is my ex mil. She’s is basically a bag of bones. Prides her self on eating 2 roast potatoes in a day. Then will gasp ‘ you’ve eaten ALL THAT!’ When it’s just a normal plate.

She is massively under weight and her son my ex was obese - until he had his stomach done.

I actually said once after she basically calling me greedy and my ex calling me a ‘machine’ regarding me finishing my dinner that I was the only one in the room with out a eating disorder

My mother is a size 22. Fuck knows how as she claims to have never been able to finish a meal. It's the weirdest thing ever.

No matter what she eats - 'oh, there was too much, I couldn't get through half of it.'

Rightio. This is the woman who criticises me every time she sees me for being too thin.