What is a positive way to help diffuse those comments away from your kid? Or better, shut them down?
In our case, dd1 (who is 6) has a lot of otherwise 'playful banter' from her grandma (MIL) about her 'fat butt' or they're constantly comparing weight, always commenting about how much or little she eats. It bothers me (& dh) a lot. SIL has had eating disorders and major struggles with her own body image over the years. MIL's self-concept is not what either of us consider healthy in the first place. Theres a lot of focus on the right weight and being skinny, and not on looking good as yourself or being healthy.
Our time we spend with MIL is limited, due to other reasons too, but we don't like navigating this and she has always had a tendency to ignore us saying "her comments won't kill her" or not taking us seriously when dh has actually stepped up to say something. I get concerned that we aren't dealing with it well, at times, and I really hate to see how it will escalate as she gets older.
Are there any good books out there for talking with dd (which is most important, IMO) or good ways you've dealt with family members making such comments?