I think Americans generally pay more attention to the gasoline they put in their cars than to the food they put in their mouths. We are a society of excess, and one of our more impressive excesses is the way in which we eat and what we choose to put in our mouths.

We are the leading country in the world in almost everything, yet our mortality rates, our cancer rates, and our neonatal death rates don’t rank among the best in the world. We lead in research, we lead in academic training, we lead in freedom of information, yet we don’t lead in taking care of our health.

We have all the knowledge in the world about everything in life, but that has made no impact on our health. Why? I think nutrition is part of the reason, and I think I know why.

No one is ever taught about nutrition. We certainly don’t teach the subject in grammar school, and it’s rarely taught in high school. Some colleges may offer it as an elective. But our parents certainly don’t talk to us about carbohydrates and proteins the way they do about the birds and the bees. If you combine this lack of knowledge with our appetite for diversity, taste, and presentation, what you have is a lot of people who know nothing about the food on their plate.

It’s never too late to learn about nutrition. The fundamental issue with nutrition is learning how to balance your caloric intake with the number of calories you burn. Everything we eat has a caloric value. If you take in more nutrients that contain a lot of calories and you don’t burn them up, the excess caloric energy is going to be stored as fat, and you’re going to gain weight. That weight and that fat will then interfere with all the normal functions of your body.

On the other hand, if you consume too few calories, say fewer than 1,200 calories a day, then your body doesn’t have sufficient energy to maintain adequate functioning. The caloric intake for a normal adult should range between 1,500 and 2,000 calories a day.

The body requires certain nutrients in order to work properly. Nutrients are the chemicals our body gets from food. These nutrients are used to build muscles, improve cell-to-cell transmission, and manufacture hormones. In describing nutrients, the word “essential” means that the body must consume them; it cannot produce them on its own. The nutrients we need include:

Essential amino acids
The body requires amino acids to produce new body proteins and replace damaged proteins to build and maintain the body.

Vitamins and minerals.
These are recognized as essential nutrients that are specifically linked to the functionality of cells. If we’re deficient in vitamins and minerals, we develop a weak immune system, cell metabolism disorders, premature aging, scurvy, goiters, and bone loss.

Fatty acids
Also essential, fatty acids are crucial for maintaining the body’s normal health. They are responsible for the normal formation of hormones and creation of some of the biological pathways responsible for dealing with inflammation and cell repair.

Sugars
They are essential because they provide the fuel our cells need to function adequately, which allows the other nutrients to be utilized properly. If cells don’t have the sugar molecule necessary to generate the energy required for repairing, functioning, transmitting, and utilizing nutrients, then cellular damage and disease will result.

Each nutrient carries out one or more unique tasks your body needs to function. And because you need many nutrients to stay healthy—protein, fat, carbohydrates, vitamins, minerals—you have to eat a wide variety of foods to get them all.

It’s when we don’t recognize the necessity of all those elements that we begin getting into trouble. It’s like filling your gas tank with gasoline and forgetting to change the oil every 3,500 miles, or forgetting to put water in the radiator. The car needs the gasoline, the oil and the water, all in the proper proportions, in order to function properly. The same is true of the human body.

The problem, as I’ve mentioned before, is that about one-third of all American meals are prepared foods. And the problem with prepared foods is that their contents are not nutritionally balanced.

Our lack of knowledge of nutrition, combined with our obsession with processed foods, is really damaging our health. So we have to get back to fundamentals, a good example of which is the diet of people who live in the Mediterranean. Their diet is well balanced with vegetables and fruit, fish and lean meat, and the good unsaturated fats like olive oil.

Today, many people think that if they stick to low-fat or nonfat foods, they won’t gain weight. That’s a myth, because gaining weight has to do with calorie intake. If you take a salad and you add cheese and eggs and everything else in the book, even if you select low-fat ingredients, you’re still consuming a tremendous load of calories. And size matters, too; the size of your portions does make a difference in terms of the total amount of calories consumed. It’s just a plain mathematical calculation.

There are no magical foods that are going to help you burn calories or increase your cell metabolism either. There is no such a thing as a food that is more active in the body than others. People think that eating a grapefruit each day or having cabbage soup for lunch is going to burn off their fat. But that’s a myth. There is only one way to burn off those extra calories: exercise, any exercise at all.

Dr. Manny Alvarez serves as Fox News Channel's senior managing health editor. He also serves as chairman of the department of obstetrics/gynecology and reproductive science at Hackensack University Medical Center in New Jersey. Click here for more information on Dr. Manny's work with Hackensack University Medical Center. Visit AskDrManny.com for more.