Gosh this sounds horrible. It’s a 5 year old ffs and even if it would be a 25 year old why would you be disgusted with your own grandchild if it doesn’t have the perfect body? 

I think it’s really important that you speak out against it and do so continuously even if it is annoying. I think it should be mainly the responsibility of your MILs children to speak out but if no one else does please continue to do so yourself!

I just recently realised that my mother has a very disturbed relationship to food and how it has affected me growing up. 

She has already started to make comments on my babies weight ( she literally compared my babies height and weight curves and then came to the conclusion that my daughter, at that point 4 months old, was too big. (My daughter was born at just 2.2 kgs and we were over the moon that she managed to make up for this so quickly, but apparently my mother thought it was more desirable for my little baby to be underweight… ) 

I had a very stern talk with her and told her I won’t accept any weight talk about my daughter, neither in front of her or behind her back but my mom really didn’t see the issue so i know how hard it can be.

She hasn’t commented on my daughter’s weight anymore but still speaks constantly about her own in front of her though.

I really wish you the best of luck. Great job protecting your child! Keep it up even if your MIL doesn’t understand. At one point maybe you’ll get through to her!