To continue on with part two of the macronutrient series, let's talk about dietary fats. First off, what is a dietary fat? A dietary fat is defined by Health Link as "the fat and oil found naturally in animal and plant foods, and those used in cooking, at the table, and added to processed foods which are made up of fatty acids." All dietary fats begin with a fatty acid, which is a long strand of hydrocarbons and an acid group. Fats from plants and animals that we eat will be in the form of triglycerides, which is composed of three fatty acids plus a glycerol backbone. I'm a visual learner, so I included an image below that shows the structure of the fatty acid and triglycerides. The R is used in the 3 Fatty Acids image to make the image more compact but it would really have a long chain of Carbons and Hydrogens attached to it (like in the second image). Understanding the structure is NOT important in the grand scheme of things, these are simply there so you can see just how complex these fats truly are.
Fat that is not used for energy is stored as triglycerides in plants, animals, and humans. When we eat dietary fats, our digestive system breaks these triglycerides down into fatty acids, remake them into triglycerides, and some are then broken back down into fatty acids and used for energy while the fats not needed are stored. When the body does not need fat for energy, it stores the excess fat as triglycerides inside of the fat cells (adipocytes), other cells, or it can be used for cell membranes. When we eat in excess of what our body needs regularly, our body cannot use all of the stored triglycerides, which can lead to increased risk of stroke, heart disease, obesity and problems associated with obesity, according to the Mayo Clinic. This means, we want to get enough to do all of the great things fat does in our bodies, but not too much that it can harm us.
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Why are dietary fats important?
According to the American Heart Association, dietary fats can be broken down to given energy, support cell growth and form cell membranes, help with nutrient absorption (especially the fat soluble vitamins A, D, E, and K), protect your organs, keep your body warm, and produce some hormones! Including healthy fats into your meals also helps you feel full and satisfied.
What are the different types of fats?
Unsaturated Fats are fats found as a liquid at room temperature but begin to turn solid when the temperature is lowered and are typically found in vegetables/vegetable products They contain at least one double bond (shown in the image below). Unsaturated fats can then be further separated into polyunsaturated and monounsaturated fats. Polyunsaturated fats include Omega-3 fatty acids, which the body cannot make and must be found in foods. These fatty acids can be found in fish, shellfish, fish oil, flaxseed, soybean oil, rapeseed oil, and walnut oil. Omega-6 fatty acids are found in corn oil, safflower oil, and sunflower oil. Monounsaturated fats include olive oil, peanut oil, and canola oil, avocados, and nuts.
Both polyunsaturated and monounsaturated fats provide Vitamin E, a powerful antioxidant that many are lacking.
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Saturated fats are fat sources such as animal fats, butter, lard, some nuts, coconut, cheese, whole and 2% milk, and palm oil that will remain somewhat solid at room temperature. These fats have only single bonds. Saturated fat in proper amounts is not bad for you, but unsaturated fats are the healthier option. Replacing large amounts of saturated fats with monounsaturated in the diet may lead to a decreased possibility of type 2 diabetes and lower the "bad" LDL cholesterol.
Trans fats are also split into two categories, naturally occurring and artificial trans fats. The naturally occurring type is found in some animal products in very small quantities but the largest amount of trans fats eaten comes from the process of adding hydrogen to vegetable oils to make them more solid. These artificial trans fats are typically found as partially hydrogenated oils. These are the fats we typically want to stay away from because it raises your bad cholesterol and lowers your good cholesterol which can then lead to other health problems.
Will dietary fats make me "fat"?
20-35% of your daily calorie intake should be from fats, but only about 5-6% of your total fat intake should come from saturated fat according to the AHA. All dietary fats are 9 calories per gram, meaning that unsaturated and saturated fats are equal in terms of the calories they provide. According to the American Heart Association, Saturated and Trans fats may lead to heart disease and stroke. At the end of the day, too much fat in general will cause weight gain because of the increased amount of calories being consumed. When choosing fats, try to stay with the monounsaturated and polyunsaturated fats (mainly vegetable based fats-avocados, nuts, oils that are liquid at room temperature). Remember, everything in moderation, even healthy, unsaturated fats can be bad for you if you're eating too much!
What are some of my favorite types of fats?
Avocados
Hummus
Chocolate
Chia Seeds
Peanut Butter
Nuts
Coconut
Fish
Sources: Murray R and Kenny L. Practical Guide to Exercise Physiology. Human Kinetics. 2016. 23-44.
Nelms M, Sucher K, Lacey K. Nutrition Therapy and Pathophysiology. Cengage. 2016.
American Heart Association. Dietary Fats. AHA website.https://www.heart.org/en/healthy-living/healthy-eating/eat-smart/fats/dietary-fats.
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