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Home : About Your Body : Metabolic Engine

Your body is essentially a large bag of chemicals run by a metabolic engine. Foods provide the building blocks for your entire structure and help produce energy to run it.

The Big Picture: It's All about Energy
No matter how complicated it seems, the human body is really just a big bag of chemicals reacting with one another. This may seem like a scientific oversimplification, but it is an accurate definition. The only missing element is the power source: energy. This energy needed to power the body comes in the form of calories-a word every dieter is very familiar with. Simply, the calories we consume are burned or stored and used as energy on an as-needed basis.

1 gram of protein	= 4 calories
1 gram of carbohydrate	= 4 calories
1 gram of fat	= 9 calories

ATP: The Energy Courier
Most people assume that the compounds that make up our food-carbohydrates, fat, and protein-directly supply the body with the energy it needs to function. Not so. An important molecule known as adenosine triphosphate, or ATP, does. Think of the three fuels you eat as three grades of gasoline that produce different amounts of energy, and think of ATP as a battery on wheels that takes that energy to wherever it is needed. Calories = Energy. ATP is the calorie carrier.

Building Blocks
The human body and food supplied by Mother Nature have one very important thing in common-they are both composed of the same organic compounds, carbohydrates, protein, and fat. So it only makes sense that to maintain the body structure-the bones, muscles, tendons, organs-necessary for good health, we need to feed the body the building blocks designed by Mother Nature. Of course they supply our fuel source, too. But this dual role food plays is different for each of the three organic compounds.

Carbohydrates

Carbohydrates play a major role in energy creation and regulation, but they are limited in their structural contribution. They don't directly build the mortar and bricks of our bodies' construction, but they do affect the quality of the construction. For example, they protect our stomach linings from the harsh acid environment and help lubricate our joints. They also make up one of the three basic parts of DNA, which is what our genes are made of.

Carbohydrates also play an important role in the regulation and release of the hormones serotonin and insulin. Serotonin levels can affect your mood and mental clarity. Insulin is one of the key players in the fat storage game. All of these starring roles-energy production, quality of construction, and regulation-make carbohydrates like a quarterback on a football team. They are key players, and they also make some important decisions in the game.

Protein

When it comes to safeguarding our structure, protein plays the biggest role of all. If carbs are like a quarterback, protein is like the rest of the team, plus the coaches, recruiters, fans-even the stadium. Protein's structural contribution to the body is well known (e.g., muscles and bones), but what is more essential is its job as the main chemical component of enzymes. Enzymes are vital to the body because they are responsible for how fast our chemical reactions run.

Enzymes-Your Body's Assembly Lines At this moment, every single biochemical reaction occurring inside of us is dependent upon the 10,000 different enzymes swimming around in our bodies. Enzymes are not only made of protein, they are also the only substance capable of breaking down the protein that we eat and then using it to build all the protein structures in our body. This "rate of reaction" is essential for life because any enzyme deficiencies or dysfunctions can result in serious or even life-threatening health problems. Like assembly line workers, enzymes can also add new elements to existing parts or break down structures for other purposes, like growth and healing from injuries. Problems with or a lack of certain enzymes can cause problems or even serious illnesses.

Protein is the major component in such bodily structures as muscles, tendons, bones, hair, and internal organs. It is also the main chemical component of hormones, blood cells, antibodies, and important chemical messengers (like insulin). Growth, reproduction, metabolic processes, and even emotional responses are dependent on protein.

Fat

When it comes to maintaining our physical structure, fat is vital to basic survival. As much as we try to rid our diets of fat, without it the most basic structure in our bodies-the cell-could not exist. Fat's main job is to keep cells and us alive. Fat molecules make up cell walls, which are responsible for keeping cells intact and maintaining their interior environment. Our life processes all occur in watery environments, which need the natural repelling properties of fats and oils to keep everything in its proper place. Simply put, the oily cell walls keep the good watery things in and the bad ones out. You may never look at the olive oil in your Italian salad dressing the same way again!

The male and female sex hormones (testosterone and estrogen) are also predominantly constructed of a fat derivative. And fats form the basis of myelin, a substance that coats nerve cells, like the plastic insulation around an electrical wire. Cerebral palsy and multiple sclerosis are conditions caused by damage to the fatty myelin covering around nerves.

Unfortunately, fat gets a bad rap for being the lazy building block. It snuggles up under the skin, forming that infamous spare tire that develops around the waist. But unlike protein, fat prefers to burn itself off as fuel. Though fat's role as a structural requirement is relatively simple, its role in the makeup of the food we eat is quite complex. The average consumer is well aware of the endless arguments over the benefits and evils of saturated, unsaturated, polyunsaturated, monounsaturated, and trans-fats. Unfortunately much of the truth about fat has been misinterpreted or misunderstood.

Cholesterol: Fat's Building Buddy Cholesterol is many things (both good and bad), but the fat you eat and the cholesterol in your body are two different things. Cholesterol is a type of modified fat found mainly in our cell walls, but it is not a type of fat used for fuel-cholesterol has no calories. Like dietary fat, however, it has an important role. Along with dietary fat it helps form a protective coating around cell walls. It also helps build hormones, like testosterone, progesterone, and estrogen. The problem with cholesterol is that we can get too much of it. Because it is essential, the body has the ability to make the amount of cholesterol it needs on its own from fat supplies. Too much cholesterol is bad enough, but too much fat and cholesterol can collect in our blood vessels, and this is a proven lethal combination that contributes to our high rate of heart disease. Shellfish, such as crab, lobster, and shrimp, are great lean protein sources, but they contain some of the highest concentrations of cholesterol in their cell walls. The meat in shellfish is low in calories only because of cholesterol's inability to be recognized by the body as a fuel. Even though shellfish is a great source of low-fat protein, you may want to check your cholesterol level if you eat it more than two to three times a week.