5 Questions and Answers About Fat

Remember last month when I shared 5 Questions and Answers about Carbohydrates?

I sure do -- I was floored by your response! That became such a popular post that I knew I had to follow up with the rest of the macronutrients.

So, without further ado, here are five questions and answers about fat...

Question #1: What is 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 four calories per gram 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 makeup. Saturated and trans fats can hurt 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.

Question #2: What is the Role of Fat in the Body?

According to the U.S. National Library of Medicine, "The fats you eat give your body the energy needed 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.

Let's start with 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, increasing the risk of heart disease and stroke. Plus, some trans fats have been linked to increased cancer risk.

Now let's move on to 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" (source).

Question #3: What Foods Contain Fat?

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 margarine, 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.

Question #4: Should I Cut Fat Out of My Eating Pattern Completely?

No. Just like with carbohydrates, cutting an entire macronutrient from your diet is not wise. Fat still plays a key role in your body and its functions. The key is not to eat too much of it. When you do choose fats, seek out unsaturated options instead of saturated or trans fats.

Question #5: How Can I Replace "Bad" Fats with "Good" Fats?

Choosing healthful types of fat instead of unhealthful types of fat helps protect your heart and cardiovascular system, provides antioxidants to combat the effects of aging, and supports healthy neurotransmitters in your brain.

Consider replacing foods high in saturated fat – like butter, cream, and coconut oil – with foods 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, it increases 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.

By Lynn Grieger, RDN, CDE, CPT, CWC, and Judy Doherty, MPS PC II