Fat has historically gotten a bad rap; with 9 calories per gram (carbohydrate and protein both have 4 calories per gram), it has a high energy content, and eating too much of it can lead to weight gain. However, fat is an important part of a healthy diet. The Institute of Medicine has traditionally recommended that adults get 20-35% of their total daily calories from fat, but many health professionals are now disputing that range. The latest research seems to indicate that it’s the type of fat, rather than the total quantity, that has the biggest impact on health.
There are a lot of key terms when it comes to fat, and it can get confusing. Fats, also known as triglycerides, consist of a glycerol backbone bonded to three fatty acids. The main types of fats that are commonly discussed when it comes to nutrition are saturated fats, unsaturated fats, and trans fats.
Saturated fats are solid at room temperature (think butter). Chemically, the term “saturated” refers to the fact that the carbon chains of the fatty acids have no double bonds and are therefore bonded to the maximum amount of hydrogen atoms. These fats are perhaps the most controversial in terms of their effect on health. They have long been associated with increased levels of LDL (“bad”) cholesterol and an increased risk of heart disease, but some recent research has suggested that they may not be as bad as we once thought. Certain saturated fats are also gaining media attention as potentially healthier alternatives (coconut oil, anyone?). The 2015-2020 Dietary Guidelines for Americans took away their upper limit on total fat, but recommended limiting saturated fat intake to 10% (or less) of total calories. If you eat 2000 calories a day, this is approximately 22 grams. For reference, a tablespoon of butter has about 7 grams of saturated fat.
Unsaturated fats are liquid at room temperature (think oil). Unsaturated fats have double bonds in their fatty acid carbon chains, meaning that they have less hydrogen atoms than saturated fats. These chemical properties change the behavior of the molecules in the body, and replacing saturated fats with unsaturated fats is associated with lower levels of LDL cholesterol. Monounsaturated fats, found in high amounts in foods such as olive oil and avocados, have one double bond, whereas poyunsaturated fats, plentiful in tofu, nuts, seeds, fish, and vegetable oils, have two. The Dietary Guidelines do not place an upper limit on the recommended amount of unsaturated fat.
Two types of polyunsaturated fats that you may have heard of are omega-3 and omega-6 polyunsaturated fatty acids. You can get omega-3’s in foods such as fatty fish, walnuts, and flax seeds; omega-6 fatty acids are prevalent in nuts, seeds and certain oils (such as soybean oil). Both omega-3 and omega-6 fatty acids are essential fatty acids, meaning that our bodies cannot make them from precursors and we therefore need to get them from our diets. In the typical Western diet, we typically get too much omega-6 fatty acids relative to omega-3’s (mostly due to high consumption of packaged foods made with refined vegetable oils). Apart from their role in helping maintain a good blood lipid profile, omega-3 fatty acids are associated with a healthy central nervous system, reduced inflammation, and improved mood.
Trans fats. These are the bad guys, right? But why? Trans fats have a certain configuration in which two pieces of the fatty acid carbon chain are “twisted” away from each other on either side of the double bond. Manufacturers of processed foods traditionally used trans fats (commonly called “partially hydrogenated oils” in packaged foods) to improve the consistency of their products and increase shelf life. However, trans fats are detrimental to health because they raise levels of LDL cholesterol and lower levels of HDL (“good”) cholesterol.
To sum it up: don’t be afraid of fats, you need them. Just be conscious of what types of fats you’re choosing. Nutrition is an incredibly complex field, and it can often get confusing when conflicting evidence about a certain nutrient or food pattern comes out (especially when the media jumps on it). In a perfect world, we would all review the original studies (called primary sources) in order to draw our own conclusions on controversial topics. Realistically, however, not everybody has the time or interest to do that, and it can be hard to judge the quality of a scientific article on a topic if you aren’t used to reading research in that field. At the end of the day, a lot of people just want simple, practical guidelines on what to eat for good health. In that spirit, here are some ways to incorporate healthy fats into your everyday diet.
Meal Ideas
Breakfast:
Lunch:
Dinner: