Along with protein and carbohydrates, fats are a type of macronutrient.
Fat is a major source of energy. It is essential for blood clotting and muscle movement. It’s required for building cell membranes (the shells that house each of your cells) as well as the protective shields around your nerves. It helps us absorb vitamins and minerals from the foods we eat.
And yet, despite the crucial role that fat plays in our body, it is still thought of as unhealthy by many. Fats are blamed for everything from obesity and diabetes to heart disease and cancer.
Some of this is justified, but not all fats are created equal. While certain types of fat are harmful, others promote good health.
Trans fats: the ugly
Short for “trans fatty acids,” trans fat appears in foods that contain partially hydrogenated vegetable oils.
Studies have linked consumption of trans fats to heart disease, diabetes, cancer, inflammation, higher LDL (bad) cholesterol, and lower HDL (good) cholesterol levels.
Trans fats have no known health benefits and there is no safe level of consumption.
As of 2022, they are banned in the United States, Denmark, Switzerland, Austria and other countries. While UK food producers have agreed to cut trans fats out of their ingredients, there is still no outright ban and a number of foods are still thought to contain them.
Trans fats have typically been present in the following foods:
- Margarines
- Vegetable oils
- Cakes
- Doughnuts
- Pastries
- Ice cream
- Bread
- Fast food
Any product that lists “partially hydrogenated oil” contains trans fats and should be avoided.
Saturated fats: The (not so) bad
Sources of saturated fat include:
- Butter
- Whole milk
- Cheese
- Yogurt
- Coconut (oil, milk)
- Fattier cuts of beef, lamb, and pork
- Palm oil
For most of your life, you’ve probably been told that saturated fat is unhealthy, clogs your arteries, and leads to heart attacks.
But recent studies indicate that it might not be so black and white.
In 2010, a meta-analysis that included 21 studies and 347,747 subjects found no significant evidence that dietary saturated fat is associated with an increased risk of coronary heart disease or cardiovascular disease.
A 2017 journal article published in the British Journal of Sports Medicine reported that the risks of LDL (bad) cholesterol had previously been overstated, particularly when it comes to a negative effect on heart health.
Further, replacing naturally-occurring saturated fats with low-fat alternatives containing added sugar presents its own problems (you can learn more about how sugar affects your weight and health here).
So, does all this mean you should load up on saturated fat? Probably not. As with many other things, “it’s the dose that makes the poison.”
Saturated fats consumed in excess increase the likelihood of heart attack, stroke, and cardiovascular events overall.
Unsaturated fats: The good
‘Good’ fats come mainly from vegetables, nuts, seeds, and fish. They are liquid at room temperature, not solid.
There are two broad categories of beneficial fats: monounsaturated and polyunsaturated fats.
Monounsaturated fats
This type of helpful fat is present in a variety of foods and oils, including:
- nuts (almonds, cashews, peanuts, pecans)
- vegetable oils (olive oil, peanut oil)
- peanut butter and almond butter
- avocado
Research has consistently shown that eating foods that contain monounsaturated fat can improve your blood cholesterol level and decrease your risk for cardiovascular disease.
Polyunsaturated fats
Polyunsaturated fats are known as “essential fats” because the body cannot make them and needs to get them from foods. Plant-based foods and oils are the primary source of this fat.
There are two main types of polyunsaturated fats: omega-3 fatty acids and omega-6 fatty acids.
Omega-3 fatty acids are thought to decrease risk of heart disease and stroke, reduce blood pressure and positively affect mental health. Foods that include Omega-3 fatty acids include:
- salmon
- herring
- sardines
- trout
- flaxseed
- chia seeds
- canola oil
Omega-6 fatty acids have also been linked to protection against heart disease. Sources include:
- tofu
- walnuts
- sunflower seeds, pumpkin seeds, sesame seeds
- corn oil, soybean oil, safflower oil, sesame oil, sunflower oil
The bottom line
While fats, particularly unsaturated fats, are essential for good health it is important to remember that they are still high in calories.
Fat contains 9 calories per gram, whereas protein and carbs only contain 4 calories per gram.
For that reason, it is important not to overconsume fats to prevent excess weight gain.
Aiming for 30% of total calories from fat is a good place to start.