Oh please can I tell my story??!!
I have out on 3 stone in about 4 years. It comes from a history of eating disorders (bulimia) that I am in the middle of dealing with. i have stopoepd vomiting (Hurrah!!!)_ but have kept most of the bingeing. HOWEVER... not throwing up means I am way healthier, and so i am working on the bingeing bit as time goes on.
Anyway.... ac ouple of years friends of DH came to stay. The wife (who is slim) was clearly asotnished at my weight gain and she looked me up and down and said; 'I can see I shall have to teach you how to eat properly' (no word of a lie and I have just outed myself to RL friends). The enxt day I was making bacon butties for everyone before we went out hiking and she ostentatiously ate one half, and acorss the table (and while I was still eating) handed the plate back at me announcing; 'This is enough for me, and it ought to have been enough for you too'.
Thankfully I found it more amusing, although it could have sent me right back into scret voimiting....
They stayed again last year and I am still fat and she started lecturing me out of the blue about how my motto ought to be 'no excuses' and then started sending me diet and eating keo diet plans on e-mail.
She also made a big thing about saying how she was 'only 8 stone' and had lost 7 pounds on the diet. Now... we are the same height, and I have been 8 stone. Pig's arse she is 8 stone. 9 and a half maybe, but not 8.
Apparently ALL these conversations were appropriate to have at either the dinner table or the breakfast table after I had hosted them and cooked for them in my own home.
DH thinks she is a twunt and said he won't have her in the house again. I told him that actually it is an interesting expercise in human behaviour. But a few years back, yes, it would have driven me back into my eating disorder.
So competitive undereating is a thing in real life.
(waits for posters to tell me that only eating half a bacon sarnie that has been made for you by your hostess is normal).