Fats constitute about 34% of the energy in the human diet. Because fat is energy rich and provides 9 kcal/d of energy, humans are able to obtain adequate energy with a reasonable daily consumption of fat – containing foods. Dietary fat is stored in fat cells located in depots on the human body. The ability to store and use large amounts of fat enables humans to survive without food for weeks.
Some fat deposits are called as structural fats. Their pads hold the body organs and nerves in position and protect them against traumatic injuries. Fat pads on the palms protect the bones from mechanical pressure. Human body has a fat layer under the skin, that insulates the body, preserving body heat and maintaining body temperature.
Dietary fat is essential for the digestion, absorption, and transport of the fat – soluble vitamins. Dietary fats depresses gastric secretions, slows gastric emptying and stimulates biliary and pancreatic flow.
There are three major groups of fats:
- Simple lipids (fatty acids)
- Compound lipids (phospholipids, glycolipids, lipoproteins)
- Miscellaneous lipids (sterols, vitamins A, E, K)
While eating too much fat can lead to weight gain and a high risk for heart disease, getting a moderate amount of some kinds of lipids can improve your heart health and help you make nutrient-dense food choices.
Monounsaturated fats lower your blood cholesterol levels. You can get them from avocados, olives, canola oil and peanut oil, and the Harvard School of Public Health suggests getting 10 to 25 percent of your calories from monounsaturated fats, or 22 to 56 g monounsaturated fats per day on a 2,000-calorie diet.
Omega-3 lipids may lower your risk for heart disease. Alpha-linolenic acid is an essential omega-three fat, and the daily value is 1.6 g per day. Good sources are flax seed and flax seed oil, walnuts and canola oil. Try to average 250 mg per day of omega-three fatty acids, which means getting about two servings per week of fatty fish or shellfish, such as herring, anchovies, mussels, sardines or shrimp.
Omega-6 polyunsaturated fats come from vegetable oils, nuts and seeds. You can lower your cholesterol levels when you choose them instead of saturated fats, and they are good sources of vitamin E. A general guideline is to get 8 to 10 percent of your calories from these lipids, according to the Harvard School of Public Health. For a 2,000-calorie diet, this means getting 20 to 22 g per day of omega-six fats.
Saturated fats, such as in butter, fatty meats, full-fat cheese and palm oil, raise your cholesterol. Limit your intake of saturated fat to 7 to 10 percent of total calories, or 15 to 22 g per day on a 2,000-calorie diet. Dietary cholesterol, such as from egg yolks and fatty animal products, raises cholesterol levels in your blood, and you should have no more than 300 mg per day if you are a healthy individual. Have no more than 200 mg if you already have high cholesterol or heart disease. Limit yourself to 2 g trans fats, or 1 percent of total calories, because these fats raise your bad cholesterol and lower your good cholesterol.