Fat
The good and the bad
Fat is necessary in a healthy diet. Together with protein, fats help to form muscles, nerves, blood vessels and other important structures in the body. However, too much fat increases the risks of serious health problems, such as high blood pressure, heart disease, stroke, and diabetes, to name a few.
The good
Unsaturated fats are considered "good" fats, and they should be included in the diet in small to moderate amounts. Unsaturated fats are generally liquid at room temperature and mostly come from plant oils. Common examples of unsaturated fats are canola, olive, peanut, safflower, soybean and sunflower oils. Some plant foods, such as olives and avocados, although solid, contain primarily unsaturated fat.
Even more than being "good," there are some fats that are "essential." This means the body cannot make or convert them from any other components. You must get them directly from foods you eat. "Omega-3 fatty acids " are found primarily in fish (especially high in salmon, albacore tuna, mackerel, herring, and rainbow trout). "Omega-6 fatty acids " are found primarily in nuts and seeds (especially high in flax seed and relatively high in walnuts and some other nuts). Both omega-3 and omega-6 fatty acids provide essential fat and are good in small to moderate quantities.
Even "good" fats should not be consumed in large amounts because they are a concentrated source of calories and can easily lead to weight gain. A diet low in total fat, with the majority of that fat coming from unsaturated sources, tends to lower blood cholesterol levels and heart disease risk.
The bad
Saturated fats are often referred to as "bad" fats because they raise cholesterol and triglyceride levels in the body, increasing the risk of cardiovascular disease. Saturated fats are generally solid at room temperature and mostly come from animal products. Some examples of saturated fat are butter, lard, shortening, cheese, cream (including ice cream) and fats from meat. Palm oil and coconut oil, although from plant sources, are also high in saturated fat.
Hydrogenated oils or "trans-fats" are considered particularly "bad" fats. These fats come from vegetable oils that have had hydrogen added to "saturate" the fat, which changes the oil's structure to a solid and also changes the effects on the body.
In addition to making the fat more saturated, hydrogenation also produces unnatural compounds called trans fatty acids (or trans fats) that have a more rigid molecular structure than natural fats do. Many scientists believe that these trans-fats are harmful because the body cannot use them properly, and they block the important functions of the "good" types of fat.
This "hydrogenation" of vegetable oils is used by many food processing companies to make products last longer in stores and thereby save money. Unfortunately, these hydrogenated products are found in most margarine, many other spreads, and in many packaged and processed foods (cookies, pastries, chips, pudding, etc.). In addition, trans-fats are common in fast foods such as French fries, deep-fried chicken and deep-fried fish.
Fortunately, legislation has recently required food manufacturers to begin listing the amount of trans-fat in their products. Regardless, it is wise to opt for unprocessed foods and limit (or avoid) foods that contain "hydrogenated" or "partially hydrogenated" oils.
How much fat is too much?
Leading health organizations have set guidelines for fat intake at no more than 20% - 35% of total calories. For a daily intake of 2,000 calories, that means 400 - 700 calories per day should come from fat. With each gram of fat contributing 9 calories, approximately 78 grams of fat is the upper limit of fat recommended per day. This corresponds to an average of 25 grams of fat per meal (assuming 3 meals per day). To put this into perspective, one tablespoon of oil contains 13 grams of fat, so the total fat should be under 2 tablespoons per meal.
In addition to total fat intake, it is recommended that no more than 10% of the total calories consumed in a day should come from saturated fat sources. Assuming 2,000 calories per day, fewer than 200 calories (22 grams) should be from saturated fat. This averages about 7 grams of fat or about ½ tablespoon of saturated fat per meal.