 Hello everyone. My name is Maya Adam and I'm a medical doctor who teaches courses on child health and nutrition at Stanford University. Before I decided to study medicine, I spent 10 years as a professional ballet dancer in Germany. I had started dancing when I was 8 years old and by the time I finished high school, I knew that I wanted to dance professionally. Being a professional ballerina was hard work and one of the things I learned quickly was that I needed to eat the right foods to give my body the energy to perform at its best. Just like you need to use high quality gasoline to run a car smoothly, your body also runs on fuel called food and if the quality of that fuel is high, your body will be able to perform at its best. Your body uses the fuel you eat to create energy and for all the amazing things that it does every day, like running, thinking, even just growing. Like adults, children are all unique and each person's body burns energy at a different rate. We measure that energy using a unit of measurement called calories and because everyone is a little bit different, there isn't one perfect number of calories that's right for every child. Even for a single child, the number of calories she might need on Monday may be different from what she needs on Tuesday, especially if she's more physically active on one of those two days. Luckily, our bodies are good at letting us know when we need to eat a little bit more or when we've had enough. It's also important to remember that food is much more than just fuel. Food is delicious and if we eat the right amount of healthy, delicious food to fuel our bodies and leave us feeling satisfied, we'll end up feeling great. Have you ever thought about where the food you eat comes from? Does it come from a nearby farm or was it flown in from somewhere far away? Do you think there's any difference between an apple that's eaten right after it's picked off of a tree or an apple that's been stored for several weeks in a refrigerator while it's being transported from a farm to a big city? When food is stored and transported long distances, it loses a lot of its nutritional goodness. Packaged foods that have been sitting on a supermarket shelf for many weeks or months are usually the least valuable sources of fuel for your body. Let me explain why. For food to last a long time on a shelf in the store, it needs to be processed. This means that the food is stripped of its nutritional value so that pests like mold won't want to eat it. When pests eat our food, we often say that the food has spoiled or gone off, but in fact the pests just got to it before we did. So when processed food manufacturers remove most of the nutrients in fresh foods, they make that food less attractive to the pests. Then, to make the food more attractive to us, they often add back a lot of fat, sugar and salt, all things that our bodies don't need too much of. These additives usually make the processed food higher in calories or food energy than fresh food. This may sound good at first, but foods that are high in food energy without providing much nutrition can leave us feeling empty and hungry again soon after we've eaten. Because processed food is high in calories but has been stripped of its nutrients, we say that the nutrient density is low. Nutrient density is just the amount of nutrition a food offers divided by its energy content. For example, a carrot has a lot of important nutrients for every unit of food energy it provides. A cookie or a piece of chocolate is lower in important nutrients, but the calories are quite high. In general, desserts and packaged foods are low nutrient density foods. Fruits, vegetables and most homemade meals are much higher in nutrient density. Here's another interesting fact. The different colors of different fruits and vegetables can actually give us clues about which nutrients are found in those foods. Orange vegetables are orange because they are high in beta-carotene, an important nutrient that protects our eyes and keeps us healthy. While dark green vegetables are rich in vitamin C and K and many other important nutrients. So, if you can, try to eat like a rainbow with different colored fruits and vegetables on your plate every day. It's okay to eat desserts and packaged foods once in a while, especially if we eat them in small amounts. But to keep our bodies running at their best, we need to try and eat high nutrient density, colorful, fresh food. Food that is as special as you are.