The problem with these messages is that each one heralds a specific body type. Be it curvy, thin, fit, or something in between, each message prioritizes one look over all others.
I think that these messages mean well. By trying to accept certain body characteristics, these messages hope to inspire women to embrace their bodies. But what happens when a young girl or even a woman sees to many "thinspo" pictures? She begins to critically analyze her own body and see only her flaws. This harmful outlook triggers eating disorders. Should the opposite of "thinspo" then be better? Not necessarily. "Fitspo" images do promote a healthier body type, however they still encourage the viewer to critically analyze their own body. It's a double edged sword. Either a woman notices there's no gap between her thighs or her biceps aren't muscular enough.
Clearly, our culture has body acceptance issues. The mainstream media needs to teach girls and women how to appreciate their own unique body. Every body truly is different. No two bodies carry weight the same way, are shaped the same way, or have the same metabolism. I don't know what the new message would be, though. "Stop hating your body" is the least descriptive of one specific body type, but I don't like its negative connotation. There should be no body hating. Only body loving.
Love your body.
From Genderly Speaking: "Skinny, Curvy, and Still not Fitting the Mold"
From Adios, Barbie: "Minnie Mouse Doesn't Need a Model Makeover"