> Food and Nutrition > Fats and Oils > essential fatty acids (EFAs)

Who would have thought that eating fat could make you thin? Well, it’s true. But there’s a catch. It depends on the kind of fat you eat.

We eat fat every day. It’s one of the three macronutrients–the other two are carbohydrates and proteins–that can be used in the body to produce energy (calories) for heat, to move our muscles and to drive all sorts of metabolic processes that keep us alive and well. Gram for gram, however, fats produce more energy than both proteins and carbohydrates (nine calories versus four for the other two). So when people decide to reduce their calorie intake to lose weight, they usually decrease their fat consumption. This is not the best approach. Energy production is the primary purpose of carbohydrates–not fats. If the carbohydrates you eat provide more energy than you burn, then the remainder gets stored as fat. Proteins and fats, on the other hand, have functions in addition to energy production and are necessary to keep us healthy.

Fats form part of the structure of our bodies and are an integral part of every cell within us. In addition, some fats can directly impact hormone activity and are used to make a whole range of substances that regulate body functions such as blood pressure, inflammation and immunity. Therefore, fat is critical to our survival, which means we need to eat it.

The Secret to Slim

The primary building blocks for most fats are fatty acids, and there are many different kinds. Some of them are beneficial to health and others are not. Polyunsaturated fatty acids (PUFAs) are liquid at room temperature and are the major components of vegetable oils such as safflower, soy bean and flax oil. Saturated fatty acids are usually solid at room temperature and are abundant in butter and lard.

In general, polyunsaturated fats are good for you. In fact, some, such as gamma-linolenic acid (GLA), can actually reduce body fat by activating brown fat stores that boost metabolism and help burn calories. On the other hand, eating too many refined, saturated fatty acids can contribute to unhealthy conditions such as cardiovascular disease, high cholesterol and triglyceride levels, type II diabetes, cancer and obesity.

Most of the processed vegetable oils that we buy in the supermarket nowadays have gone through a special processing technique that "preserves" the oil so that it can sit on the store shelf for a long time before going rancid. Unfortunately, this process changes the shape of the polyunsaturates so that our bodies no longer recognize them as the good fats. These heat-damaged fats are called "trans" fatty acids, which are also found abundantly in deep-fried foods such as french fries, potato chips and donuts. If you want to buy vegetable oils that have not been damaged by processing, visit your local health food store and purchase one that has been made by "cold pressing."

Essential Fat Facts

Two of the polyunsaturates are also called essential fatty acids (EFAs) because our bodies are unable to make them. Hence, they are an "essential" part of our diet. These are linoleic acid (LA) and alpha-linolenic acid (ALA). During the last 20 years, it has become increasingly clear that it’s not only the EFAs that are critical to our health. It’s also the other polyunsaturates that our bodies make using EFAs as starting materials. I’m going to call these "beneficial" polyunsaturated acids. Many authors refer to all of these fatty acids as essential, and this has caused some confusion surrounding the beneficial effects of certain fatty acids. Here’s why.

Linoleic acid is the parent omega-6 fatty acid, and it can be used in the body to make a whole range of "beneficial" omega-6 fatty acids. In the same way, alpha-linolenic acid is the parent of an entire series of "beneficial" omega-3 fatty acids.

This process of converting one fatty acid to another within our bodies is controlled by a series of enzymes. The efficiency of these enzymes dictates how well our bodies are able to make the "beneficial" polyunsaturates. In fact, in a healthy person under normal circumstances, only a tiny fraction of LA and ALA gets changed into the "beneficial" variety.
Beneficial Conversions

Research has proven that the first enzyme in the metabolic pathway is particularly fragile and this can severely hamper the body’s ability to make the "beneficial" fatty acids. Eating too many refined, saturated and trans fatty acids, drinking too much alcohol, smoking and some vitamin and mineral deficiencies can also slow the process. In addition, many people are naturally less able to convert essential fatty acids to the "beneficial" type, including infants, the elderly and those with atopic eczema, rheumatoid arthritis, diabetes, premenstrual syndrome (PMS) and learning disorders. These people must eat "beneficial" fatty acids directly rather than relying on their bodies to produce them.

"Beneficial" fatty acids include the omega-6 dihomogamma-linolenic acid (DGLA) and arachidonic acid (AA). These can be readily made in the body starting with GLA that is found in such foods as evening primrose oil, peanuts and eggs. The "beneficial" omega-3 fatty acids are eicosapentanoic acid (EPA) and docosahexanoic acid (DHA), both found in fish and fish oils. DGLA and EPA help control inflammation and are particularly beneficial to those with rheumatoid arthritis and PMS. AA and DHA are important membrane components in all tissues, but especially in the brain and eyes where deficiencies can alter function.

So eating the right fat is important. You can still lose weight by decreasing your total fat intake through cutting out refined saturated and trans fats and replacing a portion of that with essential fatty acids. But equally important is to make sure you get some "beneficial" fatty acids every day. Your health depends on it!

Nancy L. Morse is the co-author of nearly 30 papers in peer-reviewed biomedical journals. She has also written books on fatty acids in relation to human health.

Source: alive #232, February 2002