Our girls are pretty bad. The older girls tend to do it less, they take some from the main bowl at a time and hide it. The younger girls empty the bowl entirely and hide it in various places. They aren't great at their litter boxes yet so they tend to hide it where they sleep. Big piles of it. They eat through it and it usually is all gone and repeat when I refill the bowl. The boys take a small amount and hide that. The tiny babies don't seem to hide it yet.... But I have to feed them daily anyway since they need extra nutrition.
I don't think those that stash are more insecure. Least that wouldn't make sense with our rats. Cricket and Darjeeling (the oldest in the "young" girl cage) are not shy or insecure at all. They are in your face, on your shoulders, in your mouth (least Cricket loves my mouth). Cricket is a bit of a whiner when it comes to food, if anyone walks by her she squeeks and squalks about it. But she is just a bit of a loud mouth. Then the older girls like Sips, who are very jumpy and skiddish, don't do it as much. I think some just like to have their piles more then others.