Fats, or lipids, are nutrients in food that the body uses to build cell membranes, nerve tissue, and hormones. The body also uses fat as fuel and the fats that a person eats and aren't burned as energy or used as building blocks or stored by the body in fat cells.
Fats are the most concentrated source of calories (nine calories per gram of fat compared with four calories per gram for protein and carbohydrates) and help supply needed energy. Fat provides linoleic acid, an essential fatty acid for growth, healthy skin, and metabolism. It also helps absorb fat-soluble vitamins (A, D, E, and K), and fat adds flavor and is satisfying.
The American Heart Association recommends limiting saturated fats to less than 7 percent of total daily calories. That means, for example, if you need about 2,000 calories a day, no more than 140 of them should come from saturated fats. That's about 16 grams of saturated fats a day.
Most fats contain about the same amount of calories. Some are more harmful than others, and the three groups are saturated, monounsaturated, and polyunsaturated. All fatty acids consist of a chain of carbon atoms, with hydrogen atoms filling in the spaces around each carbon atom.
A fat is saturated when each carbon atom's spaces are filled or saturated with hydrogen atoms. Because hydrogen atoms surround each carbon atom, saturated fatty acids are compact in structure, making them highly stable, even under high temperatures. Saturated fatty acids are found mainly in animal fats like dairy and animal proteins and tropical oils like coconut and red palm oil. Your body makes some of its saturated fatty acids from carbohydrates in your diet.
Monounsaturated fats contain one double-bonded (unsaturated) carbon in their molecule. They are referred to as mono because they are not saturated with hydrogen atoms. They are typically liquid at room temperature but start to turn solid when chilled. The most common monounsaturated fatty acid in food is oleic acid, found in olive oil, avocados, and nuts. Your body also can make monounsaturated fatty acids out of saturated fatty acids.
Polyunsaturated fatty acids are missing several hydrogen atoms. They are called poly because they have more than one double-bonded (unsaturated) carbon in the molecule. These fatty acids are loosely packed and remain liquid when refrigerated. The most common polyunsaturated fatty acids found in our foods are omega-6 and omega-3 fatty acids. These fatty acids are considered to be essential fatty acids because your body cannot produce them. These fats must be obtained through your diet and include soybean, corn, safflower oils, fatty fish, seeds, and nuts. These fats can be unstable when exposed to heat and light and when compromised, free radicals are can be created.
Free radicals are referred to as free because they are missing a critical molecule and travel around the body looking to be paired up with another molecule to be complete. For the most part, antioxidants keep them under control, which your body produces naturally. Consistent exposure to free radicals is linked to the development of tumors, cardiovascular disease, premature aging, autoimmune diseases, Parkinson's disease, Alzheimer's, and cataracts.
Trans fats (or trans fatty acids) are manufactured in an industrial process that adds hydrogen to liquid vegetable oils to make them more solid. Another name for these is "partially hydrogenated oils." Companies like using trans fats in their foods because they're easy to use, inexpensive to produce, and last a long time. Trans fats give foods a desirable taste and texture. These fats are undesirable because they raise harmful (LDL) cholesterol levels.
No discussion about fat would be complete without discussing cholesterol. Cholesterol comes from animal foods and is produced by the liver. LDL cholesterol is considered the "bad" cholesterol because it contributes to plaque. This thick, hard deposit can clog arteries and make them less flexible, causing a condition called atherosclerosis.
HDL cholesterol is considered the "good" cholesterol because it helps remove LDL cholesterol from the arteries. It is believed that HDL acts as a scavenger, carrying LDL cholesterol away from the arteries and back to the liver, where it is broken down and passed from the body. HDL cholesterol contributes to cell strength, makes hormones that benefit from stress, is essential for healthy bones and muscles, digestion of fats, and bile production. It also acts as an antioxidant, protecting us against cellular damage, leading to heart disease and cancer
There are, of course, many schools of thought about which fats are best when cooking. In Ayurveda, the premiere fat is Ghee, considered the best all-around choice in small amounts. If you cook with vegetable oils other than coconut or red palm, the order of preference would be olive, peanut, and sesame, which have the highest percentages of oleic fatty acid, the relatively stable monounsaturated fatty acid.
Below is a breakdown of most cooking fats and oils: