If a guy loses interest in you he may , he may stop calling or texting you and stop being physically affectionate with you.
You may know what he is like when he is relaxed, therefore, so you may notice when he is acting far more nervously around you - either through his body language or speech for example.
It can be tough to predict which situations or topics of conversation might make someone else might feel weird, and it can be even more difficult to pick up on the subtle And yet, the more we can pay attention to their body language, the more seamless our social interactions can be.
He has all the information he needs to follow up, or not, as he wishes.