The reason I wanted to find out about what turn out to be pumpkin seeds goes back some time - to when I was a teenager.
I met an Iranian Kurd who introduced me to pistachios that he had brought from his homeland. He told me that they were eaten by prostitutes sitting in the streets outside their houses when they were waiting for clients to take an interest. You could always tell their chairs, he said, even when the prostitute wasn't there, because of the pile of shells underneath. And the reason they ate these nuts? Because they took more calories to open than the calories they contained, so the prostitutes could snack all day (or possibly night) and not put on weight.
This story didn't make sense to me since pistachios are not very difficult to open and they are probably full of calories. But, pumpkin seeds would seem to fit the bill entirely. So Scunner may well be right in his supposition. I shan't enquire how he happened to come by this knowledge.