Hunger-satiating hormones like leptin tend to vary from person to person, it's one of the things that some scientists think accounts for "genetic" weight differences (beyond caloric intake...obviously calories in/out determine weight). Also if you lose weight, you tend to stay hungrier for up to two years after the weight loss, it ties into set point theory of weight that people often talk about.
I have sympathy for people trying to lose weight for that reason.