Fat is the most energy-dense of the main nutrients, and the fatty acids are the most important components of fat. The type of fat we eat is important to the composition of fat in our bodies.
Why do we need fat?
Fat is found in all membranes and cell structures and is important for maintaining them. Fat is also important for the production of hormones and hormone-like substances such as eicosanoids. Fat tissue also isolates and protects inner organs.
The fat the body does not metabolise or use in other processes is called stored fat or triacylglycerol. If the body has too much stored fat, we become overweight. The fat surrounding the cells is called membrane fat or phospholipids. Cholesterol is another important type of fat. We need all the different types.
The most important component of the fat is the fatty acids. There are three main types: saturated fatty acids, monounsaturated fatty acids, and polyunsaturated fatty acids. What separates these fatty acids is their chemical structure. Saturated fatty acids have no double bonds. Monounsaturated fatty acids have one double bond. Polyunsaturated fatty acids have two or more double bonds. Monounsaturated and polyunsaturated fatty acids are often called unsaturated fat.
There are saturated fatty acids in all types of food, but they are especially prevalent in butter, cream and cheese. A high intake of saturated fatty acids can lead to an increased risk of cardiovascular disease.
Monounsaturated fatty acids are found in many different products, but are especially abundant in olive oil.
Polyunsaturated fatty acids are found in several different types of food, especially vegetable oils and marine oils. There are two types of polyunsaturated fatty acids that our body cannot produce itself: linoleic acid, which is an omega-6 fatty acid, and alpha-linolenic acid, which is an omega-3 fatty acid. These are called essential fatty acids and must be added through our diet. Omega-3 in fish oil is called marine omega-3. Omega-3 in plants is called plant-based omega-3.
According to the Norwegian Directorate of Health, 25–35 percent of the energy we consume through our diet should be fat. Globally, the percentage of fat in people's diets varies greatly. In Norway, about 35 percent of energy comes from fat, whereas the intake is less than 20 energy percent in some developing countries.
Status in the population
The population's intake of saturated fat fell from 17 to 14 energy percent between 1970 and 1990, and it has remained stable at this level for many years. The mortality rate of cardiovascular disease also fell during this period. In recent years, the percentage of saturated fat has increased to about the same level as in 1970.
Measuring fatty acid status
By measuring the composition of fatty acids in the red blood cells, we can find out what type of fat the person has eaten.