Oatmeal is one of the best things you can eat in the morning because it's high in fiber and promotes a lasting feeling of satiety. By filling up on the right foods from the start, you can go out and conquer your day without pesky hunger pangs. Plus, you won't be tempted to overeat at lunchtime, letting you dodge the afternoon slump. Try overnight oats, or add oatmeal to your yogurt with lots of fruit and healthy grains.