Fats, also called lipids, are provided in the diet from such sources as animal protein, butter, oils, nuts, and many refined products. Fats are often thought of as bad, a myth perpetuated by the many fat-free products flooding store shelves. However, fats are needed in appropriate amounts for normal functioning in the body.For example, lipids are the main component of each cell in your body. In addition, fat is a major source of energy, especially when you are at rest or performing low- to moderate-intensity physical activity. Excessive consumption of fat is unhealthy, but concerns also arise when fat intake is too low. A balanced approach to fat intake will provide the necessary amount of fat for optimal health.
Fats are present in a number of forms, including saturated fats, monounsaturated fats, and polyunsaturated fats. These designations have to do with the chemical structure of the fat. Trans fats are found naturally in some animal products (mainly meat and dairy products), but also are a result of a manufacturing process called hydrogenation. Hydrogenation changes the structure of a fat to make it more stable, and as a result more like saturated fats (which are solid at room temperature). Food companies hydrogenate fat to increase the shelf life of the product, to make it taste more like butter, and to save money because it is less expensive to hydrogenate oil than it is to use butter.
In general, health concerns result from consuming too much saturated and trans fats. Trans fats have been shown to increase the bad cholesterol in blood (low-density lipoprotein cholesterol, or LDL-C), even more so than saturated fats. Sources of trans fats include animal products, margarine, and snack foods. The good news is that, as a result of health concerns, the food industry is reformulating many products to remove or at least reduce the amount of trans fats. Many restaurants have also now gone "trans fat free." Companies that make processed food products are required to list the amount of trans fat in their products. Although some products have labels that state they are "trans fat free," this actually means that they contain no more than 0.5% trans fat.
Monounsaturated fats, such as olive oil, canola oil, avocados, walnuts, and flaxseeds, have been shown to be protective against heart disease and type 2 diabetes. That is not to say that you can consume as much monounsaturated fat as you want; however, selecting monounsaturated fats instead of saturated fats may lead to better health (e.g., healthier blood cholesterol levels).
Polyunsaturated fats, such as safflower oil, corn oil, and fish oils, have also been shown to be protective against many diseases. Fish oils (eicosapentaenoic [EPA] and docosahexaenoic [DHA]) have been shown to decrease inflammation within the body, and may protect against heart disease, type 2 diabetes, and arthritis. This does not mean that EPA and DHA are protective against everything, but they are important to overall health. Therefore, you should try to consume 2 to 3 ounces (57 to 85 g) of fatty fish (e.g., tuna, salmon, and sardines) at least two days per week.Fish oil supplements may also be warranted (consult with your health care provider to see if this is appropriate for you).
Saturated fats are found in products such as butter, cheese, meat, palm oil, and whole milk. Because of the increased risk of disease associated with saturated fats, less than 10% of your calories should come from saturated fat,with an even better target of less than 7%.Trans fats also should be limited to as little as possible. Because of the focus on saturated and trans fats, the nutrition labels on food products include total fat as well as the amount of saturated and trans fats.
Although not technically a fat, cholesterol is in the lipid family and is found in animal products. Your body needs a certain amount of cholesterol, and thus, even if your diet contained none, the liver would produce what your body needs. The problem arises when cholesterol levels in the blood become too high. Total blood cholesterol levels, as well as LDL-C levels, are definite predictors of heart disease. Although you consume cholesterol in your diet, a major factor influencing your blood cholesterol is the amount of saturated and trans fats you consume. Thus, limiting saturated fat intake to no more than 10% of your calories is recommended (no more than 7% is even better) as well as keeping your consumption of cholesterol to less than 300 milligrams per day.
Total fat intake should be between 20% and 35% of calories.Most of these calories should come from monounsaturated and polyunsaturated fats (e.g., fish, nuts, vegetable oils), and your consumption of saturated fat should be limited.
Excerpted from ACSM's Complete Guide to Fitness & Health (Human Kinetics, 2011). For more information on ACSM's Complete Guide to Fitness & Health, or other health and fitness resources, visit www.HumanKinetics.com