What is fat?
Fat is one of the macronutrients in human nutrition. Many people automatically associate fat with butter, lard or the greasy substances attached to animal meats. However, plant oils, which are liquid at room temperature, are fats too. Fat represents the most complex group of nutrients. There are many types of fats, some good and some bad. No natural food is made up of only one single type of fat.
What are the functions of fat in the human body?
Fat stores excess energy from your diet for later use. One gram of fat provides 9 calories, the highest of all nutrients. Fat also serves as the building material for cell membranes and as a precursor for signaling molecules. Two particular types of fats, omega-3 fatty acids and omega-6 fatty acids, also play important roles in the regulation of gene expression (the turning on and turning off of genes).
What are the major types of fat?
There are three major types of fats in the human diet: saturated, unsaturated and trans-fats. Since saturated fats can increase cholesterol levels in human blood, they are often called the “bad fats.” Unsaturated fats, including MUFA (monounsaturated fatty acids) and PUFA (polyunsaturated fatty acids), are often considered “good fats” because of their associated beneficial effects. However, not all unsaturated fats are created equal. For example, omega-3 fatty acids and omega-6 fatty acids are both PUFAs but have opposite effects when it comes to chronic disease risk. Trans-fats cannot be properly broken down into energy by your body and are associated with the greatest increases in cholesterol and fat tissue build-up. Therefore, trans-fats are the “worst” dietary fat. More details about the types of fats and their effect on human health are described in Fat Metabolism 101. Table 1 lists common fatty acids in the diet.
Table 1.Common fatty acids in the human diet.
| Types | Common Name | Structure | Source | |
|---|---|---|---|---|
| SATURATED FATS | Lauric | C12 : 0 | Coconut oil, palm kernel oil | |
| Myristic acid | C14 : 0 | Milk, coconut oil | ||
| Palmitic acid | C16 : 0 | Palm oil, milk, butter, cheese, cocoa butter, animal meat | ||
| Stearic acid | C18 : 0 | Palm oil, milk, butter, cheese, cocoa butter, animal meat | ||
| UNSATURATED FATS | MUFA | Palmitoleic acid | C16 : 1 | Marine animal oil |
| Oleic acid | C18 : 1 | Olive oil, canola, most dietary fat | ||
| omega-6 PUFA | Linoleic acid (LA) | C18 : 2 | Corn, soybean, sunflower seeds and peanut oils | |
| Arachidonic acid (AA) | C20 : 4 | Peanut oil. Small amount in meat, dairy products and eggs | ||
| omega-3 PUFA | α-Linolenic acid (ALA) | C18 : 3 | Flaxseeds oil, olive oil, rapeseeds oil (Canola) | |
| Eicosapentaenoic acid (EPA) | C20 : 5 | Fish oil, marine algae | ||
| Docosahexaenoic acid (DHA) | C22 : 6 | Fish oil, marine algae | ||
How much fat do I need in my diet?
The Dietary Guidelines for Americans’ recommended Acceptable Macronutrient Distribution Range (AMDR) for fat intake is between 20 to 35% of total dietary calories for adults age 19 and older. The AMDRs for fat are the same for both men and women, but are higher for younger ages (Table 2).
Table 2. AMDR for fat for different age groups
| Age (years) | AMDR (% of total energy intake) |
|---|---|
| 1-3 | 30-40% |
| 4-18 | 25-35% |
| ≥ 19 | 20-35% |
How can I improve my diet with healthy fats?
We recommend using the GB HealthWatch Diet and Nutrition Evaluator to get the most accurate estimate of your current fat intake. Depending on your genetic background, health status and personal goals, you may want to maintain, increase, or decrease your fat intake.
In general, you should aim to increase your intake of “good” fats and decrease your intake of “bad” fats. Avoid trans-fats (the “worst” fats) as much as possible since trans-fats can accumulate in the body and cause long-lasting and harmful effects. Trans-fats are normally found in deep-fried junk foods like fried potato chips and French fries, and certain artificial-fat substitutes such as margarine. In the United States, products that contain less than 0.5 g trans-fat per serving can list the trans-fat content as zero per serving on the Nutrition Facts label. You will need to read the ingredients section on the product to see if the food contains hydrogenated or partially hydrogenated oils which are the main sources of trans-fats. If these ingredients are used, you should avoid the food.
Also try to limit the amount of saturated fats (“bad” fats) in your diet. Animal fats from red meat and full-fat dairy products normally contain high levels of saturated fats as well as high levels of cholesterol. Plant oils can be sources of large amounts of saturated fat as well. For example, coconut oil and palm oil are composed mainly of saturated fats and should be limited in your diet. Other plant oils, such as corn oil, peanut oil and sunflower oil, have an imbalanced omega-3:omega-6 ratio. These oils contain high levels of omega-6 fatty acids but little or no omega-3 fatty acids. Long-term consumption of these oils may increase your risk for inflammation and chronic heart disease.
To get the amount of fat you need for a healthy diet while at the same time avoiding excess saturated fat, opt for healthier plant oils, such as olive oil or canola oil when cooking. These oils have a high percentage of unsaturated fatty acids (the “good” fats) and a balanced omega-3:omega-6 ratio. You can also get “good” fats from deep sea fish like salmon, and seafood like oysters. These foods have high levels of omega-3 as well as high quality proteins.
To reduce fat intake, you should limit fat-rich foods, such as those shown in Top Foods. You should also choose fat-free dairy products, select lean meats, and trim off as much fat as possible when consuming animal-based foods. Keep in mind most salad dressings are very high in fat. Pay attention to the amount of salad dressing you use to avoid excess fat intake from this seemingly “healthy” dish. See the article What’s Wrong with Salads for a better understanding of this issue.
