Fats are also called lipids. They are a group of chemical compounds that contain fatty acids. Chemically fats are called triglycerides because the fat molecules are composed of a backbone molecule of glycerol to which three fatty acids are attached.
Expressing the energy value of foods
|*kcal/g is kilocalories per gram. Sometimes the term Calories/g is also used with “C” in uppercase. Both are correct and 1 kcal = 1 Cal. When we loosely say 1 Calorie, actually we mean 1 kilocalorie.|
Energy is stored in the body mostly in the form of fat because of its high energy density in comparison to carbohydrates (see the table above). Fat is also needed in the diet to supply essential fatty acids that are substances essential for growth but which body is not able to produce. The terms fat and fatty acids are frequently used interchangeably.
We saw in the table above that 1 gram of fat gives us 9 Calories—more than twice the calories given by the same amount of carbs or protein. For disease control less is better in case of fats of certain types—for example saturated and trans-fats. There are several categories of fats: The good, the bad and the ugly! There are saturated, unsaturated fats and also trans-fats. There are essential and non-essential fats when viewed from nutritional angle.
There are three main categories of fatty acids: saturated, monounsaturated and polyunsaturated. Fatty acid molecules are chains of carbon atoms with hydrogen atoms attached to the carbon atoms.
All natural fats that we eat including animal fats and plant based fats are a mixture of all the three categories mentioned above and usually dominated by one category.
When all carbon atoms are saturated by single bonding with hydrogen atoms, as well as with other carbon atoms, the fatty acid is called saturated. There is a lot of controversy about the goodness and badness of saturated fats. The old belief is that saturated fat is responsible for the formation and progression of atherosclerosis (formation of plaque on the inner walls of the arteries) and consequently heart disease. But a recent meta-analysis published in the American Journal of Clinical Nutrition in 2010 found no link between consumption of saturated-fat and enhancement in the risk of coronary heart disease or cardiovascular disease. See the conclusion:
"Conclusions: A meta-analysis of prospective epidemiologic studies showed that there is no significant evidence for concluding that dietary saturated fat is associated with an increased risk of CHD or CVD. More data are needed to elucidate whether CVD risks are likely to be influenced by the specific nutrients used to replace saturated fat."
According to old school of thoughts, saturated fats should not exceed 10% of your total daily calorie intake. Animal fats are the major sources of saturated fats. Vegetarianism is therefore health-promoting.
In a fatty acid chain, if there is a carbon-carbon double bond due to absence of two hydrogen atoms, it is called mono-unsaturated fatty acid (MUFA). For disease control, and health maintenance, one should consume MUFAs in place of saturated fats. MUFAs are heart friendly.
Oleic acid is present in all foods that contain fat. Due to the presence of the double bond at the center of the oleic acid molecule, it is capable of maintaining the critical nature of fluidity of the membrane matrix of body cells.
Formation of foam cells along the arterial walls is an important stage in the development of atherosclerosis (plaque). Oxidized LDL cholesterol helps transform the macrophages (types of cells) into foam cells. Oleic acid resists this process and thus retards the process of atherosclerosis. Oleic acid is therefore heart-healthy
Oleic acid is not an essential fatty acid because body can transform stearic acid into oleic acid
1. Meta-analysis of prospective cohort studies evaluating the association of saturated fat with cardiovascular disease; Patty W Siri-Tarino, Qi Sun, Frank B Hu, and Ronald M Krauss; Am J Clin Nutr March 2010 91: 535-546;
You may also be interested to read the following relevant information about fats:Composition of Fats