fiber and hunger

So they say that fiber is filling and puts off hunger... The past 2.5 weeks, with my diet dominated by whole grains and legumes, I've been easily not-eating for 12 to 16 hours between last meal (probably too late) and first meal the next day. But last night, last meal was that Portuguese food, largely white bread and white rice. And despite having felt stuffed, just 9 hours later I was too hungry to get back to sleep -- while the two slices of whole wheat bread I had then, just 120 calories, have coasted the next 6.5 hours, and I'm still less hungry than I was then.