A: If you ate a meal three to five hours earlier, have a 100- to 200-calorie snack, says Linda Spangle, author of 100 Days of Weight Loss. That's about 10 percent of your daily calorie intake and just enough to boost blood sugar and help prevent overdoing it at your next meal. Before you start eating, however, be sure you have rumbling in your belly, not just boredom on the brain. "You need to train yourself to recognize true hunger signals—growling stomach, fatigue, slight headache. When you feel those signals, it is time to eat. If you ate within the last two hours but are staring at the refrigerator, go do something else for 10 minutes and see if you still feel hungry."