Fat grams are considered essential for the daily functioning of the body and the brain, and typically should be included in the diet as a primary source of energy. They also play a role in proper brain development, nerve transmission, hormone production, and the ability of the body to repair itself. There are four types of fat grams: monounsaturated, polyunsaturated, saturated, and trans fats. Approximately 30 percent of daily calories should typically come from fat grams, with the majority coming from unsaturated fats.
Studies have shown that unsaturated fats in the diet contribute to a healthy body. On the other hand, saturated and trans fats can cause disease and should be consumed in moderation. Doctors usually refer to the unsaturated fats as good fats, and the saturated and trans fats as bad fats.
Monounsaturated fats are usually liquid at room temperature. Studies have shown that unsaturated fats help maintain a healthy body by lowering cholesterol and reducing heart disease. They can be found in olives, cashews, and pumpkin seeds.
Polyunsaturated fats contain omega-3 and omega-6 fatty acids, which protect against heart disease. Like monounsaturated fats, polyunsaturated fats are usually liquid at room temperature. They can be found in fish, sunflower seeds, and corn.
Generally, saturated fats are solid at room temperature. Saturated fats increase cholesterol levels and are associated with heart disease and hypertension. Examples include eggs, dairy, and the fat on meat. Even though saturated fats occur in nature, large amounts of them are not considered part of a healthy diet.
Trans fats are synthetically produced. They were invented to increase the shelf life of packaged food. Trans fats have no nutritional value and consuming too many may lead to weight gain. Generally, trans fats are found in deep-fried foods and packaged snack or junk food, such as chips and cookies.
Each fat gram contains nine calories, compared to four calories in a gram of protein or carbohydrate. A calorie is a measurement of energy expenditure. The more calories that are consumed, the more energy is needed to burn them.
When more fat is consumed than expended, it is stored in fat cells. Fat can be stored in the organs or under the skin. Stored fat under the skin acts as a cushion and insulation against the cold. In organs, stored fat can lead to heart disease and type 2 diabetes. Too much stored fat, in general, can lead to obesity.
The recommended daily allowance (RDA) of fat in the diet is approximately 30 percent for adults. Less than seven percent of daily calories should come from saturated fats, and less than one percent of daily caloric intake should come from trans fats. The remaining 22 percent of fat in the diet should come from unsaturated fats.
Generally, the number of fat grams consumed affects the percentage of total fat in the daily diet. Nutritional labels on foods in the United States are required to list fat grams per serving. The type of fat — unsaturated, saturated, or trans — is also required to be listed.
Terms such as low-fat, reduced fat, and lite are relative and do not actually indicate a particular number of fat grams. By law, as long as a food has 50 percent fewer fat grams or one-third fewer calories than the regular version, it can be classified as low-fat. The term fat-free indicates that one serving has no more than .5 grams of fat per serving.