It's hard because obviously a healthy body is 'best' in terms of health outcomes and just ability to live easily
Eg, I'm 5'3. My optimal weight looks wise is around 9 and a half stone. I'm 10 at the moment and thats ok. When I got up to nearly 12 stone a few years ago, I started to really feel it physically - I was out of breath, my knees hurt and I was starting to adapt how I did things when getting dressed.
I don't want to live like that. I want to be able to do things easily and live without pain so I lost the weight.
But I'm very pragmatic about it. I don't equate a person's size/weight with their worth as a person. My partner is teetering on obesity and has done his whole life. From an aesthetic/attraction perspective, it doesn't make any difference to me but I do worry about his health and that is a genuine concern not a shallow appearance based concern dressed up as a health concern. Because he was that size (actually bigger) when I met him and I fancy him regardless.
My son gained weight after leaving home through bad eating habits. Nothing else. He's worked hard at changing his eating habits and exercise and lost the weight. I've never commented on that and only ever spoke about it when he brought it up. But, again, I was genuinely becoming concerned about his health so it was hard not to say anything at all because if he were smoking or drinking excessively, there'd be no problem with me bringing that up as a concern. In fact, I'd be expected to.
When my daughter was younger, there was a lot of talk around not focusing on girls' weight but only commenting on their bodies in terms of what they could do and how strong they were. But that is still commenting on their bodies!
She did a lot of gymnastics and loved showing off her muscles and her 6 pack. She still does gymnastics but less often/intensely so no longer has a 6 pack. She's also put on a few pounds due to university living. But it's only noticeable to me because she was so athletic before. Again, I wouldn't dream of commenting (and she'd rightly put me back in my box if I did!)
But she's also only 4'11 and has a very small frame. I would be concerned for her health if she started gaining a lot of weight. Not because it would reflect badly on me that I had a 'fat' child but because I love her and I want to her be healthy and not have her life restricted in any way by weight related difficulties.
My exh (her dad) became very overweight/obese and developed several health issues related to that. His mum is very overweight and has similar health concerns. Potentially, life limiting ones. With several in patient stays at hospital and daily medications. His dad and brother are healthy weights and have none of these health issues. I know which I'd choose for my daughter.
Constant snippy criticisms are obviously wrong, but we shouldn't be afraid of general discussions around weight and health with people we love.