Planning a balanced diet can be like a juggling act.

Food fuels your body, just like gasoline fuels a car. But, unlike the family car that is probably limited to three grades of unleaded fuel, people are faced with a lot of food choices -- perhaps too many choices. In fact, some scientists believe that these choices are helping make our population the largest - in physical size - that we've ever been. Nutrition is the study of these choices.

Nutrition has a major effect on everything about you - including how you think. It has been said that breakfast is the most important meal of the day. This is especially true for school goers. Studies show that eating breakfast can boost your memory and even your grades. Snacks are important too. You or some of your classmates might start to feel tired or find it difficult to concentrate late in the morning or in the early afternoon. This could be because you skipped either breakfast or lunch. Or, perhaps you didn't eat enough. Or maybe you could have made a better choice about what you did eat. If you did eat a healthy breakfast and still feel this way, you might just need a snack to refuel.

Food choices can have a major impact on the rest of your body too. Right now, there are close to 10 million children aged 6 years old or older in the United States who are obese. This means that they are beyond being overweight - medically speaking they have excessive body fat in proportion to their height. The number of obese children aged 6 to 11 years old has tripled over the past three decades here in the United States! Our nation's teenagers aren't doing much better. The rate of obesity among 12- to 19-year-olds has doubled in the past 30 years. Poor nutrition is certainly to blame. Of course, there are other factors too - like as a nation, kids today are not getting enough exercise. But still - nutrition is a huge factor.

Obesity is a serious issue. Alone, it can make you feel overly tired or sluggish - limiting what you are physically able to do. You might have trouble breathing and/or sleeping. And, it can lead to a number of other health problems, including diabetes and cardiovascular disease. So, what can you do about it? It all goes back to the choices mentioned earlier.

Between all the advertisements you see and hear, you're blasted with hundreds of images of soda, chips and candy every week. And, if you're like loads of kids around the country, there are vending machines stocked with these items at your school. You might even have one or more familiar fast food franchises selling lunch at your school cafeteria. With options like these readily available, it's not difficult to see how obesity is such an issue.

STOP! Step away from the... Instead of feeding your sweet tooth with cookies, cake or ice cream, have some of these tasty treats: Top graham crackers, gingersnaps or rice cakes with a small amount of nut spread (like peanut or almond butter) or flavored cream cheese. Top angel food cake with fresh berries. It's only about 180 calories so you could save an incredible 350 calories or more! Top plain, unsweetened yogurt with fresh fruit and a little low-fat granola or make a smoothie using fresh fruit and skim milk (or yogurt). For all of these, not only will you be reducing you calorie and fat intake, you'll also be getting some nutritional benefit from things like fruit, nuts and cheese.

Soda, chips, candy, and overly-processed and fried fast foods all have something in common - they're chock full of "empty" calories. Meaning that, for the most part, they're providing you with little or no nutritional value. Even if they seem to make you full or satisfy your hunger, they're not really filling you up energy-wise. Eating this stuff isn't going to refuel you for the long haul. But before you get too worried, no one is saying you can never have soda, chips, candy or fast food. You just need to eat and drink those things in moderation. And balance them with "good for you" foods to make sure you're getting enough of the things your body needs and not too much of what it doesn't.

To achieve or maintain a healthy weight, your body needs a certain number of calories from a combination of seven basic components: carbohydrates, proteins, fats, vitamins, minerals, fiber and water.

Carbohydrates and proteins are healthier sources of calories than fats. Our bodies do need a certain amount of fat to function properly -- an adequate supply of fat allows your body to absorb the vitamins you ingest. But, as mentioned earlier, an excess of fat can have serious health consequences. A diet of fresh, natural food usually provides all of the vitamins and minerals that you need.

Hunger So how does your body know that it is time to eat? Where does the sense of hunger come from? It's not from a rumbling stomach -- people who have their stomachs removed still feel hungry. It appears that a small brain structure called the hypothalamus is the center of hunger. If one part of the hypothalamus is damaged, a person will overeat tremendously. If another part is damaged, a person never gets hungry. So clearly these two parts balance one another to produce the sense of hunger.

So now that you know what it is your body needs, let's talk about how to figure out how much to give it. It's actually pretty easy. First, consider how old you are. Second, think about how much time you spend each day exercising or participating in some type of aerobic activity (like playing basketball, volleyball or field hockey). Third, consult a reputable source, like the United States Department of Agriculture. They're the people who created the Food Guide Pyramid - now known as the MyPyramid Plan.

Fortified Processing tends to destroy vitamins. That's why you'll find that many processed foods are "fortified" with man-made vitamins.

For example, let's say you are a 12-year-old girl who gets between 30 and 60 minutes of exercise every day. The MyPyramid Plan (http://www.mypyramid.gov/) suggests that you take in a daily total of 2,000 calories comprised of:

• 6 ounces of grains (a source of carbohydrates, dietary fiber, vitamins and minerals)
• 2 ½ cups of vegetables (a source of carbohydrates, dietary fiber, vitamins, minerals and water)
• 2 cups of fruits (a source of carbohydrates, dietary fiber, vitamins, minerals and water)
• 3 cups of milk (a source of vitamins, minerals and protein)
• 5.5 ounces of meat and beans (sources of protein)
• 6 teaspoons of oil (fats)

Then, figure out the total amounts per food group. Create a pie chart representing the food groups. Compare the first menu you created to this fast food menu. Compare the calories and the pie charts.