The glycemic load is key. This is the measure of how quickly a food containing carbohydrates turns into glucose. Studies have shown that when a kid eats a high-glycemic meal, his blood-glucose surges and then plummets -- leaving him even hungrier. A low-glycemic meal takes longer to digest so a child's blood sugar stays steady, and he'll feel full longer. In general, low-glycemic carbs have more fiber and are less processed.
Choose lots of veggies and fruits (but not all of them). No surprise here: You should pile on the produce. However, corn and potatoes have a high glycemic index, and certain tropical fruits, such as bananas and pineapple, are more likely to contribute to weight gain than apples, grapes, oranges, cantaloupe, kiwi, or berries.
Try to include protein in most meals and snacks. In addition to being filling, protein stimulates the release of a hormone that helps the body release stored fat to use for energy, says Dr. Ludwig.
Fat isn't always the enemy. Healthy fats like unsaturated oils, nut butters, and avocado slow down digestion, and they make fruit, veggies, and whole grains even more filling. Fat is actually vital to health: It's needed to make cell membranes throughout the body -- and the types of fat your child eats affect his immune system, nervous system, and overall health.
Avoid foods that your great-grandparents couldn't have recognized. Fake foods (think chicken nuggets, fruit roll-ups, cheese puffs, and other highly processed products bearing no resemblance to anything found in nature) are rarely healthy choices, says Dr. Ludwig. When you choose grains, look for the least-processed options, such as stone-ground wheat bread, steel-cut oatmeal, and brown rice.
Food can affect behavior, too. When your child's blood sugar drops soon after a high-glycemic meal, she also has a surge in the stress hormone adrenaline. That can make her cranky, irritable, or unable to focus in class.
Kids don't have to feel deprived. No parent wants to put their child on a diet. But if the whole family focuses on low-glycemic eating, one child who has a weight problem won't feel singled out. By helping him focus on the quality of the food he's eating rather than the quantity, he can eat until he feels satisfied and still lose weight. For more information, go to endingthefoodfight.com.