Try and drink some water until your stomach is full. It doesn't really make you feel full but it can't hurt! :)
Henrietta's suggestion is a good one. A HUGE glass of ice cold water or ice cold water sweetened with something like diet, decaffeinated tea or Crystal Light, is always good! If you still have the munchies, I recommend oatmeal! LOL! It sounds corny, but it works. One package of plain instant oatmeal has 100 calories. Sweeten it with cinammin, Splenda and maybe even some fruit like raisins or a banana. If you are the type where you know you'll get the munchies around 9-10 p.m., eat a slightly smaller dinner so that you can have this oatmeal later on. Sometimes you need more than one packet of oatmeal, but the total calories may still only be 200-300 - and it's ridiculously healthy. Eat the oatmeal slowly and you'll see how full you'll become!
Not to mention that it is also an excellent source of fiber and helps to lower your cholesterol!!
I say go with the water. Nice and cold. Fills you up and has no calories. H20 is the perfect diet aid!
