Fat contains more than twice the amount of energy as carbohydrate. A single gram contains nine calories making it a valuable source of fuel for longer duration activities. While fat cannot supply energy quickly enough for very intense activity, it can be used by the body to power lower intensity exercise such as jogging and walking.
Fat also provides insulation and protection to vital organs such as the heart, lungs and liver and transports vitamins throughout the body.
Not all dietary fat is the same. Like carbohydrate, fat can be broken down into several different groups:
Saturated fats are found in foods such as red meat, egg yolks, cheese, butter, milk and commercially prepared cakes, pies and cookies. The typical western diet consists of almost 40% total fat. Of this, 15% is made up of saturated fats, which is considered a major cause of coronary heart disease, diabetes and other degenerative illnesses. No more than 10% of the diet should come from saturated fats.
Unsaturated fats come in the form of monounsaturated fats and polyunsaturated fats. Monounsaturated fats can actually lower the risk of coronary heart disease and are found in foods like olive oil, canola oil, avocados, almonds and pecans. Polyunsaturated fats, found in sunflower oil, safflower oil and corn oil are not thought to contribute to heart disease but don't offer the same protection as monounsaturated fats.
Essential fatty acids are a class of polyunsaturated fats that have received a lot of attention in the media recently. They are thought to be cardio-protective and may help prevent a range of other illnesses. There are three types of essential fatty acids - Omega 3, Omega 6 and Omega 9. Omega 3 and Omega 6 must be consumed while the body can produce some Omega 9 on its own. Essential fatty acids are required for healthy cardiovascular, reproductive, immune, and nervous systems. Found in foods like walnuts, pumpkin seeds, Brazil nuts, sesame seeds, avocados, some dark leafy green vegetables and oily fish, the typical Western diet is often deficient of essential fatty acids.
Despite its bad press, cholesterol is actually essential for many important bodily functions. There are essentially two types of cholesterol - low-density lipoprotein (LDL) and high-density lipoprotein (HDL). LDL is known as the "bad" cholesterol because it carries and then deposits cholesterol at the artery walls. HDL on the other hand, is known as "good" cholesterol because it acts as a scavenger removing cholesterol from artery walls and transporting it to the liver to be excreted.
Although some foods like cream, butter, ice cream, egg yolks, shellfish and red meats contain cholesterol, it's a high intake of saturated fat that causes the body to synthesize too much cholesterol. The maximum amount of dietary cholesterol recommended each day is 300mg.