There are such things as good fats!

Fats are not all bad for your health. In fact, fats can be thought of as “the good, the bad, and the ugly”.

Why do we need fats in our diet?
Dietary fats are an essential part of a healthy diet. They provide us with essential fatty acids, which the body is unable to synthesize itself. We need fats for energy, to protect our organs, and to help keep us warm. Fats are needed to absorb some nutrients (e.g., fat-soluble vitamins like vitamin A, vitamin D, and vitamin E) and they are important for proper cell structure and function, blood clotting, muscle movement, inflammation, and the production of many important hormones (1, 2).

What are the different types of fat?
There are four major dietary fats in food (1). The “good fats” are monounsaturated and polyunsaturated fats, the “bad fats” are saturated fats, and the “ugly fats” are trans fats.

These different types of fats all have nine calories in every gram of fat, while carbohydrates and proteins contain four calories per gram. If you consume too many calories, regardless of the source (good fat, bad fat, protein, or carb), it can lead to weight gain. But if you consume high levels of “the bad” and “the ugly” fats, you also increase your risk of heart disease and stroke. This is because these fats raise bad LDL cholesterol levels (1). For more information about LDL cholesterol, see our previous article “Bad” versus “good” cholesterol.

The different types of fats have different structures, which is why some fats (the good ones) are liquid at room temperature, while the bad ones are solid at room temperature (2). It is all to do with the bond formation between the carbons in the fats (3).

  • Unsaturated fats contain one (mono-) or more (poly-) double cis bonds, therefore they can’t bind to as many hydrogen atoms and there is a bend at each double cis bond.
  • Saturated fats contain only single bonds, therefore the carbon atoms are bound to as many hydrogen atoms as possible (i.e. they are saturated with hydrogens).
  • Trans fats are also unsaturated but the double bond is a trans bond (instead of a cis bond). This results in a straight chain (rather than a bent chain like the unsaturated fats).

This article focuses on “the good” monounsaturated and polyunsaturated fats.

Monounsaturated fats
Good sources of monounsaturated fats include:

  • Olive oil
  • Peanut oil
  • Canola oil
  • Avocadoes
  • Most nuts

The Mediterranean diet is a diet that is high in monounsaturated fats (olive oil) and is associated with a low rate of heart disease, despite being a somewhat high-fat diet (2).

Polyunsaturated fats
Polyunsaturated fats are essential fats, which means they are required for normal functions (e.g., making cell membranes) but the body is unable to produce them so must obtain them from dietary sources. The two main types of polyunsaturated fats are omega-3 fatty acids and omega-6 fatty acids (2).

Omega-3 fatty acids have a wide range of health benefits, including reducing blood pressure, raising good HDL cholesterol, and lowering triglycerides–all things that help prevent heart disease and stroke (2). Good sources of omega-3 fatty acids include:

  • Salmon
  • Sardines
  • Flaxseeds
  • Walnuts
  • Canola oil

Omega-6 fatty acids also offer protection from heart disease (2). Good sources of omega-6 fatty acids include:

  • Safflower oil
  • Soybean oil
  • Sunflower oil
  • Corn oil

The “bad fats” and the “ugly fats”
Saturated “bad fats” are common in the American diet and are found in red meat, whole milk, cheese, coconut oil, and many commercially prepared foods. A diet high in saturated fats is associated with higher cholesterol levels, particularly increased bad LDL cholesterol levels, which increase the risk of atherosclerosis and heart disease. Most experts recommend limiting saturated fats to under 10% of calories a day (2), with the American Heart Association recommending just 5-6% of calories from saturated fats (4).

See our previous article here for more information about atherosclerosis.

Trans fats are the worst type of fat. Some trans fats are naturally occurring (from some animal products), while other trans fats are produced artificially by adding hydrogen to liquid vegetable oils to make them more solid. Trans fats raise bad LDL cholesterol, lower good HDL cholesterol, and are associated with a significantly increased risk of heart disease and stroke, as well as an increased risk of type 2 diabetes (5).

How can I check my cholesterol levels?
We offer a range of at-home tests for checking the impact of your diet on your cholesterol levels. See the Related Tests section at the bottom for all the tests that we have available. Each of these tests just requires a tiny blood sample from a self-collected finger-prick. No need to make a doctor’s appointment for sample collection and your results are available online as soon as testing is complete.

1. Dietary Fats. (Reviewed Nov 2021). American Heart Association.
2. The truth about fats: the good, the bad, and the in-between. (Dec 2019). Harvard Health Publishing, Harvard Medical School.
3. Marchand V. (2010). Trans fats: What physicians should know. Paediatr Child Health. 15(6): 373-375.
4. Saturated Fat. (Reviewed Nov 2021). American Heart Association.
5. Trans Fats. (Reviewed March 2017). American Heart Association.