Body Positivity: the word gives men the image of a fat woman sitting on the couch eating ice cream and watching tv. The truth is, you've all got your definitions wrong.
What I think about body positivity is that, instead of loving your body because you think it looks good, love it because of all the life experiences and everything it can do. Your legs, no matter what they look like, can take you to the tops of mountains, your hands can touch so many fluffy animals and build things, your arms can hug so many people who need it.
While it is unnatural to hate your body, healthy habits are what enable it to do good things. There's nothing wrong with loving how it looks, but that is not necessary and shouldn't be your soul focus of life.
Hating your body can lead to eating disorders, which of course aren't only caused by self hate. Anorexia and bulimia are the most well known eating disorders, but there are of course others. Eating disorders aren't about weight, however; eating disorders don't have a look. Someone who looks completely healthy could have an eating disorder, especially bulimia (classified as b/ping).
They can be caused by many different things, such as wanting to have control over some aspect of their lives, or to prove they can do something against their biological needs. I did it because I wanted to be sick and feel pain and control, and weight is a thing that can be controlled.
Body positivity is also not only about weight. Stretch marks occur on the huge majority of women, and on some men too. Scars, for example self harm scars, are often seen and judged very heavily by the public. Body positivity supports being comfortable with your physical body in how it looks but as well as its function.
Change for yourself, not others.
My point is, body positivity isn't what many men think it is. It is appreciation of what your body can do rather than hating or loving it only because of how it looks, and body positivity is about supporting healthy habits to foster a strong body. Body positivity supports all differences, not just differences in weight.