People these days display a negative attitude towards fat, but they should realize that body fat plays a vital role in the three major functions of all nutrients: to build body structures, to help regulate metabolism, and to provide a source of energy.

What are fats?

We are going to help you understand the vital role of fat in your body by going through some of the facts and fallacies surrounding fat in the diet and fat usage during exercise.

What are fats needed for?

First then, let us look at the role of fats in the human body. Even if you eat no fat or oil at all, your body will make up for the lack by “manufacturing” some out of carbohydrates and proteins. Fat or oil are one of the elements which are necessary to all cells and tissues. The others are proteins, carbohydrates, minerals, vitamins and water. The human body can not do without any of these.

Fats are used in the manufacture of hormones, such as testosterone and estrogen. Phospholipids are also involved in the process of blood-clotting.

You can plainly see that without dietary fats, your body would stop functioning. You need to ensure that you have a nutritionally sound mixed diet, and that you do not go pursuing fad diets which eliminate fat. If you do follow these fad diets, you’ll end up lethargic and in poor health, and probably won’t even get leaner as your body will want to conserve its fat stores for use in vital metabolic roles.

How does fat get into your body?

Dietary fats are known as lipids. Ingested lipids are digested primarily in the small intestine by the actions of a variety of enzymes (such as lipase, the enzymes which act on lipids), with the assistance of salts from the bile.

Lipids are broken down into fatty acids, glycerol, cholesterol, and phospholipids which are then absorbed into specialized cells of the intestinal walls, which recombine them into fat droplets made up of fats and proteins. This “lipoprotein” is then pushed into the lymphatic system which scoops up the fat droplets and transports them to the bloodstream for distribution.

Saturated and unsaturated Fats

Polyunsaturated and monounsaturated fat are both unsaturated fats.

Foods containing monounsaturated fats are gaining recognition for their benefits in the fight against heart disease. It is known that saturated fats will raise blood cholesterol, whereas polyunsaturated fats can help to lower cholesterol.

People in Mediterranean countries, with a diet consisting largely of cereals, vegetables and olive oil, have a low incidence of heart disease. Olive oil contains mostly monounsaturated fats.

However, it seems that diets which are very low in fat or which contain mostly polyunsaturated fat will also lower HDL cholesterol. This HDL cholesterol protects against heart disease, and therefore a higher level is beneficial.

Diets containing monounsaturated fats will lower total cholesterol, but will maintain or improve the HDL cholesterol level thus giving a more desirable ratio.

Food sources of monounsaturated fats include avocado, olives, olive oil, and many nuts and seeds. Lean meat contains about equal amounts of monounsaturated and saturated fats.

Liquid vegetable oils, like soy, corn oil or sunflower oil are high in something the scientists call polyunsaturated fatty acids. Animal fats such as meat and dairy products and solid vegetable shortening are low in polyunsaturated fatty acids.

A healthy diet contains a variety of foods including plenty of cereals, grains, vegetables and fruit, moderate amounts of lean meats and dairy foods, and small amounts of fats, sugars and alcohol.

Can your body manufacture fats?

Yes, your body can convert proteins and carbohydrates into fat. Proteins, carbohydrates and fats are all basically long chains of carbon, hydrogen and oxygen atoms that can be recombined to form different shapes.

Even if you cut down on dietary fat, you still need to address the total energy value of the food you still eat. If your total energy intake is greater than your energy expenditure, then the excess amounts of both proteins and carbohydrates will be converted into fat. So it is not just what you eat, but also how much you eat and how active you are that determines your level of stored body fat.

How fat is used in the body for exercise?

When you get down to the basics, your body uses all the available energy sources (carbohydrates and fat) all the time. The mix changes depending on how hard and how long you have been working. Fats are the normal fuel, and carbohydrates are like a turbocharger that cuts in when high intensity work needs to be done.

At low intensities of exercise, say up to 75 percent of your maximum heart rate, about 50 to 70 percent of the energy used derives from body fat using the aerobic energy system. As you exercise harder and harder, the contribution of fats as a fuel decreases and the contribution of carbohydrates increases.

If you do lots of aerobic exercise your body will get better at using fat as a fuel. If you exercise regularly at high intensities, then your body becomes less efficient at using fat as a fuel.

If your muscles are working so hard that they are producing lactic acid (the effects are an increasing heart rate, muscle fatigue, dizziness, spots behind your eyes, and/or queasiness), then the lactic acid in the bloodstream may block the release of fat from the fat stored in your adipose tissue. If you cannot get it out of your fat stores, you cannot burn it up to get leaner!