I also have dinner around 5pm these days. The way I've understood the effect: your body cannot go into a state of rest until it's finished "processing" all of t

I also have dinner around 5pm these days. The way I've understood the effect: your body cannot go into a state of rest until it's finished "processing" all of the food you ate, and that process can take a while. So even if you fall asleep on a full stomach, your body is not in a restful state yet.