Is he interested when he's looking at you for a long time or when he's going out of his way to avoid eye contact and turn his back towards you?

For example a guy at my gym that I like is always turning his back towards me and avoid eye contact, but he looks at other guys and girls.
Is he interested when he's looking at you for a long time or when he's going out of his way to avoid eye contact and turn his back towards you?
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