I get very hungry at night. I have several theories on this, they are...
I drink alot of diet lemonade at night- none in the day time, its all water till I get home. I watched a documantary saying that if we drink diet drinks, the body still expects just the same calories as if it were full sugar, so craves and craves it until you eat it.
I exercise quite late in the day...am not perfect, I don't always eat afterwards (its a long anorexic hang up you don't want to hear about) but if you do also exercise for anything more then an hour, eat something, take on some protein and carbs, it doesn't need to be massive amounts but just within an hour after exercising and low fat, low sugar low salt.
Tierdness can lead to hunger. Apparently (no evidence for this- someone (a neurologist) told me this) the hormones goven off when we have had enough sleep are similar to those we get when we eat. The body craves them and this is a reason for feeling more hungry then normal. But I find it impossible to sleep if I am hungry so not sure that works for everyone- maybe see if it works for you?
Do you drink enough water during the day? its easy to confuse hunger with thirst at times and I'd imagine harder to distinguish when your tierd.
Stress- at the end of the day we are left with loads of "stuff", this increases adrenalin (sp!) which can mean you crave more sugary carbohydrate type foods.
Also, check your nutrient intake for the rest of the day- check you got enough protein, complex carbs, enough fruit and veg, enough nutrients. If you didn't it could be your body is craving them.