I think feeling sad like that is a sign that food has taken on way too much importance in one's life. Maybe as eating normalizes, that feeling will go away.
Imagine that you're someone who brushes their teeth after every meal, and the last time you brush them for the day you feel sad because you won't get to brush them again... that might seems just a little strange?
So it's just an indicator of what food means... I've experienced it, too... because for me, munching in the evening has gone along with relaxing, enjoying, feeling better. I still plan a snack for the evening for this reason, but now it's a snack that fits with my daily calories.
Jay