ABC's of Fat

Fats in foods supply calories and essential fatty acids. They also aid the absorption of fat-soluble vitamins like vitamins A, D, E, and K.  Fat, carbohydrates, and protein are the three macronutrients in our foods that provide calories used for energy. Fats provide more calories per gram than any other calorie source — 9 calories per gram instead of the 4 calories per gram that you'd find in protein and carbohydrates. There are four different types of fat:

1. Saturated fat
2. Trans fat
3. Monounsaturated fat
4. Polyunsaturated fat

Each type has different physical properties based on its chemical make-up. Saturated and trans fats can have a negative impact on heart health and are usually called "bad" fats, while both types of unsaturated fats can be good for you in moderation and are thus called "good" fats.
All types of fat contain the same number of calories per gram.

The fats you eat give your body energy that it needs to work properly.  You also need fat to keep your skin and hair healthy. Fat also helps you absorb vitamins A, D, E, and K, the so-called fat-soluble vitamins. Fat also fills your fat cells and insulates your body to help keep you warm.  However, the types of fats that you consume can have varying effects on your health.

The Bad Fats

Saturated fats increase your risk of heart disease, and, according to the Dietary Guidelines for Americans, they should be used in small amounts and replaced by foods higher in monounsaturated and polyunsaturated fatty acids to promote cardiovascular health. MyPlate adds a bit more detail, asserting, "Saturated fats and trans fats tend to raise 'bad' (LDL) cholesterol levels in the blood. This, in turn increases the risk for heart disease." Trans fats from partially-hydrogenated oils can also lower HDL cholesterol levels, which further increases the risk of heart disease and stroke. Plus, some trans fats have been linked to an increased risk of cancer.

The Good Fats
  
Unsaturated fats (both monounsaturated and polyunsaturated) can actually help lower your LDL (a.k.a. "bad") cholesterol levels. Both omega-3 and omega-6 fatty acids are polyunsaturated fats, and your body needs these in order to keep your brain healthy. Omega-3s can also help successfully control triglyceride levels (more good news for your heart) while omega-6s are key for blood sugar regulation. Monounsaturated fats are usually good sources of vitamin E, which is necessary for healthy vision, a healthy immune system, and other benefits.

Animal fats tend to have a higher proportion of saturated fatty acids (seafood being the major exception), and plant foods tend to have a higher proportion of monounsaturated and/or polyunsaturated fatty acids (tropical oils being the exception).  The primary sources of saturated fat in an American eating pattern are cheese, pizza, desserts, chicken, and processed red meat like sausage and ribs.

The bulk of our trans fatty acid intake comes from processed foods filled with  the partially-hydrogenated oils used in some margarines, snack foods, and prepared desserts.

Monounsaturated and polyunsaturated fats are usually liquid at room temperature and are found in seafood, nuts, seeds, avocados, olives, and liquid oils. Oils high in monounsaturated fatty acids include canola, olive, peanut, sesame, and safflower oils. Other foods that contain these healthful fats include avocado and  most nuts. Oils that are good sources of polyunsaturated fatty acids include soybean, corn, and cottonseed oils. Other foods that are rich in these polyunsaturated fats include flaxseeds, along with salmon, tuna, and other fish.

Because they are high in calories, many people try to cut fat out of their diet completely.  It is not wise to cut an entire macronutrient from your diet. Fat still plays a key role in your body and its functions. The key is to simply not eat too much of it. When you do choose fats, seek out unsaturated options instead of saturated or trans fats.

Choosing healthful types of fat instead of unhealthful types of fat helps protect your heart and cardiovascular system, provide antioxidants to combat the effects of aging, and support healthy neurotransmitters in your brain. Consider replacing foods that are high in saturated fat – like butter, cream, and coconut oil – with foods that are high in polyunsaturated fat and monounsaturated fat – like olive oil, nuts, and seeds.

For example, you could replace a fatty cut of beef with a piece of salmon, or sauté some vegetables in olive oil instead of butter.  Also, reduce sources of saturated and trans fats in general. Try buying skim or 1% milk instead of whole milk. Do the same with cheese, yogurt, and milk-based puddings. It's also possible to lighten up the cuts of meat you purchase, choosing chicken breasts over thighs, lean beef over fattier cuts, etc.  At the same time, increase sources of unsaturated fats. Add ground flaxseed to your oatmeal and then top it with walnuts, or add a slice or two of avocado to your tuna sandwich.

Adapted from article By Lynn Grieger, RDN, CDE, CPT, CWC and Judy Doherty, BS, AOS, PC II in 
From Food and Health Communications Newsletter article 5-questions-and-answers-about-fat