Guys, How do I know if he's genuine?

Iv been really close with this guy lately who I met online and he's admitted to have developed feelings for me and I feel the same obviously, we are planning on making things serious and meeting up, but iv tried my best to get back into shape (to the xtreme) and when he realized id been doing this becuase I was scared of what he thought, he said he doesn't think I should diet because he doesn't care for my weight, he thinks I am beautiful and perfect just as I am. How do I know he really means this? and that he's generally interested not just saying that to get sex or sumthing? (Im not obese or anything by the way I'm origionally curvy and proud but I had put on some extra weight from a contraceptive)
Guys, How do I know if he's genuine?
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