Fats are important macronutrients. There are several types of dietary fat, and some are much more healthful than others.
Fat is essential for several bodily functions. It is an energy source, and it protects the skeleton and nerves. Fat also makes it possible for other nutrients to do their jobs.
However, not all dietary fats are equally beneficial:
- Saturated and trans fats can raise cholesterol levels and increase disease risk.
- Unsaturated fats support health and may be monounsaturated or polyunsaturated.
Meats, dairy products, snack foods, and baked goods contain saturated and trans fats. Some sources of unsaturated — healthful — fats include nuts, oils, seeds, and avocados.
Below, we take an in-depth look at the different types of fats, including which are most healthful and which foods contain them.
Fats are classified in a range of ways, depending on their attributes:
- Fats or fatty acids: These terms can refer to any type of fat, but “fats” usually describes those that are solid at room temperature.
- Lipids: This can refer to any type, regardless of whether it is liquid or solid.
- Oils: This can describe any fat that is liquid at room temperature.
- Animal fats: Among these are butter, cream, and fats in meats, such as lard.
- Vegetable fats: Among these are the fats in olives and avocados, as well as olive, peanut, flaxseed, and corn oils.
Fats are an important part of the diet for humans and many other animals. The body stores fat for protection, warmth, and energy.
Regardless of the type, all fats have the same number of calories — 9 calories per gram — compared with less energy-dense carbohydrates and proteins, at about 4 calories per gram.
Different types of fat influence health in different ways, particularly blood and heart health.
The next sections take a closer look at the effects of various fats on the body.
Saturated fats are solid at room temperature and are sometimes called solid fats. The basic carbon structure of these fatty acids is “saturated” with hydrogen atoms.
Saturated fat may increase health risks if a person consumes too much over a long period.
The American Heart Association (AHA) recommend that people eat no more than 13 grams of saturated fat per day.
Some sources of saturated fat include:
- animal meats and meat products
- dairy products, except those that are fat-free
- processed foods, including baked goods, snack foods, and french fries
- some vegetable oils, including coconut oil, palm oil, and cocoa butter
Instead, a person should replace sources of saturated fat with more healthful foods, such as nuts, seeds, avocados, beans, whole grains, and vegetables.
Unsaturated fats are liquid at room temperature, and they mostly derive from plant oils. Healthcare professionals consider these to be “good” fats.
The two main types of unsaturated fat are:
Monounsaturated fat molecules are not saturated with hydrogen atoms — each fat molecule has bonded with one hydrogen atom.
Monounsaturated fats may lower LDL, or “bad,” cholesterol levels, and maintain healthful levels of “good” high-density lipoprotein (HDL) cholesterol.
However, simply adding monounsaturated fat to the diet will not have this effect, unless a person also reduces their intake of saturated fat.
Many health professionals report that a diet rich in monounsaturated fats may also reduce a person’s risk of heart disease. The Mediterranean diet, which research suggests may reduce the risk of chronic disease, contains plenty of monounsaturated fats.
Sources of monounsaturated fats include:
- olives and olive oil
- nuts and nut butters
A number of spaces around each polyunsaturated fat molecule are not saturated with hydrogen atoms.
Nutritionists report that polyunsaturated fats are good for health, especially those from fish and algae, known as omega-3 polyunsaturated fatty acids.
The Office of Dietary Statistics say that omega-3 acids could help keep the heart healthy, reduce triglycerides in the blood, and improve brain, joint, and eye health.
Omega-3 fatty acids may protect against heart disease by lowering blood cholesterol levels and, possibly, inflammation.
That said, a large-scale Cochrane analysis found that omega-3 supplements had no significant benefits for heart health. Determining the effects with certainty will require further research.
The other type of polyunsaturated fats are omega-6 fatty acids. These mostly occur in vegetable oils and processed foods.
An excessive intake of omega-6, which is common in the standard American diet, may lead to increased inflammation.
Sources of polyunsaturated fats include:
- oily fish, such as sardines, mackerel, trout, salmon, and herring
- safflower, grapeseed, soybean, and sunflower oils
- nuts, seeds, and pastured eggs
Trans fats are manufactured. They are the product of a process that adds hydrogen to liquid vegetable oils to make them more solid. Another name for trans fats is partially hydrogenated oils.
Trans fats are not essential, and they have damaging health effects.
Trans fats raise levels of LDL cholesterol and lower levels of HDL cholesterol. This increases the risk of heart disease, stroke, and type 2 diabetes.
The World Health Organization (WHO) estimate that trans fats are linked with 500,000 cardiovascular deaths each year.
Trans fats became popular when food companies found them easy to use and cheap to produce. They also have a long shelf life and can give food a nice taste.
As trans fats can be used in commercial fryers many times over, they have become common in fast-food chains and other restaurants.
However, the WHO have called on governments to eliminate trans fats from the global food supply. Most commercial food production companies have now eliminated trans fats from their products.
Sources of trans fats can include:
- fried foods, such as french fries
- doughnuts, pies, pastries, biscuits, and other baked goods
- pizza dough, cookies, and crackers
- stick margarines and shortenings
- packaged foods
- fast foods
If any ingredient list on food packaging includes “partially hydrogenated oils,” it means that the product contains trans fats.
The AHA advise that consumption of trans fats should not exceed 5–6% of a person’s total caloric intake. However, consuming any amount of these fats increases health risks.
According to the WHO, to avoid unhealthy weight gain:
- total fat intake should be less than 30% of total caloric intake
- saturated fat intake should be less than 10% of total caloric intake
- trans fat intake should be less than 1% of total caloric intake
Health professionals recommend replacing saturated and trans fats with monounsaturated and polyunsaturated fats. Overall, the diet should be nutritionally adequate and contain enough calories to maintain a healthy weight.
Not all fats are equally beneficial. It is important to understand the differences between the types of fat, read labels carefully, and make healthful dietary choices.