Healthy, high quality fats from foods are necessary nutrients. They help build cells and maintain brain function. With infants and toddlers, whole milk fats are necessary for kidney and central nervous system development. Our bodies don't make healthy fats, so we need them in our diets. Since fats yield high amounts of calories, a little goes a long way. The average daily diet should include a ratio of 25 - 30 % fats; 10% being saturated fat, and 20 % unsaturated fat. If you have a medical condition such as diabetes or heart disease, these ratios will differ some. Follow the diet plan prescribed by your healthcare team.
Good fat, bad fat. How to tell the difference? Fats that are good for you contain monounsaturated or polyunsaturated oils and are plant based. Tropical oils, such as coconut oil however, contain high amounts of saturated fat and are NOT healthy, regardless of the trendy marketing claims. Sources of good polyunsaturated fats are avocados, seeds, and nuts. Healthy monounsaturated fats include olive and canola oils. These fats are associated with better blood glucose, blood pressure, and cholesterol control and reduce the risks of cardiovascular disease. One animal based polyunsaturated fat is the Omega-3 which comes from dark fish meat, such as salmon or tuna. Omega-3's have shown to reduce inflammation in arthritis, heart disease, COPD, and various allergies. Note: the fish itself should be fatty, not the way it is prepared. Deep-frying destroys the Omega-3 properties.
Fats to limit are in animal-based foods. These contain mostly saturated fats and include fatty meats, full fat cheeses and other dairy products such as whole milk and butter. Ways to reduce the fat without losing nutrition include: Trimming visible fat from meats before cooking. Select lean meats, avoid processed meats (lunch meats, sausage, bacon), Use fat-reducing methods of cooking, such as grilling or broiling. Use cooking spray or small amounts of cooking oil. Use low-fat dairy products, skim milk (for children over the age of 5 years) and use full fat cheeses sparingly.
Trans fats are man-made fats that are the most evil of all fats. They add shelf life to processed foods including baked goods, snack crackers, processed cheeses, margarine, shortening... Also listed on ingredient labels as partially hydrogenated oils, they are constructed by adding hydrogen to unsaturated fats to make oils more stable or "solid" as in margarine and shortening. Trans fat raises total and LDL cholesterol, increasing the risk of heart disease.
Bottom line: Butter is "better" than margarine containing trans fat, but even butter has it's limits. Moderation is key when it comes to "bad fats". Read labels. Many margarine products now-days do not contain trans fats.The general rule is: the softer the margarine, the less trans fat it contains. Avoid processed foods; they are high in "empty calories" and yield little nutritional value. Healthy fats are good, but in small amounts.
For a more complete list of foods in the "healty/unhealthy" categories see the ADA/Academy of Nutrition and Dietetics booklet Choose Your Foods: Exchange Lists for Diabetes ($3.25 including shipping; shopdiabetes.org)
~American Diabetes Assoc., 2014