Model Hailey Clauson Is Down With Plus-Size Models, But Passing On Cake

Model Hailey Clauson is all about the plus-size model movement, but only from the sidelines ... based on what she told us about her birthday celebration, anyway.

We got Hailey at LAX -- she turned 22 on Tuesday -- and she made it clear she wouldn't be indulging too much ... due to work. Translation: I don't wanna look fat for a photo shoot!

Still, she's clearly happy hers isn't the only body type killing it in modeling these days.

Bottom line? Hailey's gonna have her cake, and eat it too. Later.