From Shereen Jegtvig,
Your Guide to Nutrition.
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Fat is the substance in food that provides a rich texture and flavor. The foods that contain the largest amounts of fat come from animal products such as meat, dairy and eggs, plus nuts and seeds. Common examples of cooking fats include olive oil, lard, canola oil, walnut oil, butter, margarine and shortening.

Fat has gotten a bad reputation in the diet world, although only some of that reputation is deserved. While bad fats can contribute to poor health, some fats are needed for good health. This lesson will help you understand a little more about the fats you need and the fats to avoid.

A Little Bit of Fat Chemistry

Fats and oils are made up of individual molecules called fatty acids. Fatty acids are chains of carbon and hydrogen atoms that have a carboxyl group at one end and a methyl group at the other. Carboxyl groups contain one carbon atom, one hydrogen atoms and two oxygen atoms, and methyl groups include one carbon atom and three hydrogen atoms. The carbon atoms in the fatty acid molecules are linked by single or double bonds.

Fatty acids vary in length. Short chain fatty acids have two to four carbon atoms, medium chain fatty acids have six to 12 carbons atoms, long fatty acids have 14 to 18 carbon atoms. A few fatty acids have more than 20 carbon atoms chains.

Fatty acids are either saturated or unsaturated. Saturated fatty acids have no double bonds between any of the carbon atoms in the chain. Unsaturated fatty acids have one or more double bonds in the carbon chain. Monounsaturated fatty acids have one double bond and polyunsaturated fatty acids have two or more double bonds. Unsaturated fatty acids are sometimes named by the position of the double bonds in the carbon chain. The names omega-3,-6 or -9 refer to the locations of the first double bond in the the three different fatty acid molecules.

Unsaturated fatty acids can have two different configurations of the hydrogen atoms on either side of the double bonds. These are referred to as "cis" or "trans" configurations. Cis configurations have those hydrogen atoms both on the same side of the molecule. This causes the molecule to look like it is bent. Trans configurations have those hydrogen atoms on opposite sides of the double bond. This gives the molecule a more linear appearance, like saturated fats. Interestingly, it turns out that both saturated fats and trans fats are bad for your health.

Most of the fats in the food you eat are called triglycerides. A triglyceride is made up of three fatty acid molecules attached to a glycerol molecule. Your body will use triglycerides as a source of energy or store them as adipose tissue, better known as body fat. The types of fatty acids in the triglycerides have an important impact on the physical state of the fats you eat. Fats that are composed of triglycerides with saturated fatty acids, like meat, are solid at room temperature. Fats that are composed of triglycerides with unsaturated fatty acids, like vegetable oils, are liquid at room temperature.

The foods you eat may also include cholesterol. Cholesterol does not produce any energy like triglycerides, but it is important for many biochemical processes and hormone production. Elevated cholesterol levels in your body have been associated with an increased risk of cardiovascular disease. The cholesterol in your body is mostly made in your liver and there are three different types: High Density Lipoproteins, Low Density Lipoproteins and Very Low Density Lipoproteins. Having higher HDL cholesterol levels can decrease your risk of cardiovascular disease, while elevated LDL cholesterol will increase that risk.

Fat Functions in the Body

Fats and cholesterol have a number of important functions, which include:

• Lubrication of body surfaces
• Components of cell membrane structures
• Formation of steroid hormones
• Energy storage
• Insulation from cold
• Carrying fat soluble vitamins A, D, E, K

Saturated Fats and Your Health

Saturated fats are made up of triglycerides that have saturated fatty acids. These fats are solid at room temperature. They come mostly from animal sources, although saturated fats are in coconut oil, palm oil and palm kernel oil. Saturated fats found in red meat, butter, milk, cheese and eggs will increase cholesterol levels in the body. In fact, saturated fat will raise your cholesterol much more than dietary cholesterol does.

Eating a diet rich in red meat has been linked to an increased risk of cardiovascular disease and some cancers. Since red meat has the highest concentration of saturated fats, many experts suggest that you limit your consumption of red meat to only two or three small servings per week.