Fat is probably the most controversial macronutrient. Are fats good or bad? Maybe both? Does fat make you fat? Should you eat low-fat? High-fat? etc. etc. This guide will help clear up all of these questions and more.
This article covers everything you need to know about dietary fat, including:
- What is dietary fat?
- Why is fat important?
- Types of fat
- Healthy vs. unhealthy fats
- How much fat should you eat?
- Best sources of dietary fat
What is Dietary Fat?
Fat is the most energy-dense macronutrient, containing 9 kilocalories (aka calories) of energy per gram. This means fat can provide more than twice as much energy per unit as carbs or protein (which only provide 4 calories of energy per gram).
Fat is made up of fatty acids (the smallest building block of fat). The fat that we intake via food gets broken down into these smaller molecules called fatty acids, in the body, where they perform various functions.
Why is Fat Important?
Like any macronutrient, fat is an essential source of energy.
While fat is not the body’s primary energy source (which is carbohydrates), it is a very dense source of energy for the body to tap into if it has depleted its carbohydrate supply. Fat provides long-term energy storage.
Dietary fat can also help you feel satiated (more so than carbs) and help balance blood sugar and eating habits.
In addition to providing energy and energy storage, fat is also essential to proper micronutrient absorption and hormone production. Many micronutrients, hormones, and enzymes, are fat-soluble, meaning they dissolve in fat and hence cannot be properly absorbed without fat.
Fat-soluble vitamins include vitamin A, vitamin D, vitamin E, and vitamin K. Without adequate dietary fat intake, risk of deficiency of these vitamins increases.
Once ingested fats are broken down into their fatty acid components, they carry out a multitude of functions for the body.
A variety of fatty acids are found in our blood, cells, and tissues, where they play important roles such as providing energy, constituting membranes, influencing metabolism, responsiveness to hormones, gene regulation, and more.
Types of Fat
There are two main categories of dietary fat: saturated fat and unsaturated fat.
The difference between these two types of fat is in the structure of the fat molecules – unsaturated fats contain double or triple bonds within their structure, while saturated fats only contain single bonds.
Containing only single bonds means that saturated fats have a more rigid structure. This makes saturated fats typically solid at room temperature.
Sources of saturated fat include:
- animal meat: fatty beef, pork, lamb, poultry with skin
- animal fat: tallow, lard
- full-fat dairy products: cream, butter, cheese
- coconut oil
- palm oil
- cocoa butter
- baked goods
- fried foods
The presence of double bonds in the molecular structure of unsaturated fats makes them more flexible than saturated fats. Unsaturated fats are typically liquid at room temperature.
Unsaturated fats can be further categorized into two sub-categories: monounsaturated fat and polyunsaturated fat.
The prefix mono- or poly- simply refers to having only 1 or more than 1 double bonds in the molecular structure, respectively.
Monounsaturated fatty acids (MUFAs):
Monounsaturated fats are generally considered healthy – they have been shown to lower cholesterol and reduce risk of heart disease.
Types of MUFAs include: oleic acid (most abundant MUFA in the diet), palmitic acid, elaidic acid, and vacentic acid.
Sources of monounsaturated fat include:
- nuts and seeds
- nut butters
- olive oil, sesame oil, peanut oil, canola oil, safflower oil
Polyunsaturated fatty acids (PUFAs):
Like monounsaturated fats, polyunsaturated fats are generally considered healthy and have been shown to help reduce cholesterol and risk of heart disease.
Polyunsaturated fats also provide the body with essential fatty acids that cannot be produced by the body and must be acquired through diet.
Types of PUFAs include: omega-3 fatty acids and omega-6 fatty acids.
Omega-3 fatty acids: alpha linoleic acid (ALA), decosahexanoic acid (DHA), eicosapentanoic acid (EPA).
Omega-3 fats are important for human brain, nerve, and eye development (in infants), as well as a healthy immune system, and a reduced risk of heart disease.
Sources of omega-3s:
- fatty fish: salmon, mackerel, anchovies, sardines, arctic char, trout, herring
- flaxseeds, flaxseed oil
- chia seeds
- soybean oil
- canola oil
Omega-6 fatty acids: linoleic acid (LA), arachidonic acid (ARA), gamma linoleic acid (GLA), conjugated linoleic acid (CLA).
Omega-6 fats are important for gene regulation, immune health, and blood clotting.
Sources of omega-6s:
- safflower oil, sunflower oil, soybean oil
- nuts and seeds
- meat, poultry, fish, and eggs
Omega fatty acids are very important for the body and our health. It is important to consume a healthy ratio – the recommendation is a 4:1 ratio of omega-6 to omega-3, or lower. You don’t want this ratio too high (although it typically is way too high in the standard American diet with a ratio more like 15:1 – likely due to high omega-6s in vegetable oils which are over-consumed).
Healthy vs. Unhealthy Fats
So, which fats are good and which fats are bad? Is it true that unsaturated fats are healthy and saturated fats are unhealthy?
Well, not exactly. The reality of healthy vs. unhealthy fats is quite a bit more nuanced than this general assumption.
Polyunsaturated fats are generally considered healthy, yet vegetable oils, even though they are polyunsaturated, are not exactly good for you – here’s why: too high omega-6s, skewing the omega-6:omega-3 ratio.
And as for saturated fats, human have evolved eating natural sources of saturated fats such as animal fats.
The truly unhealthy fats, the fats you should undoubtedly avoid, are trans fats.
These are man-made fats that are created through an industrial process of hydrogenating, or partially hydrogenating, vegetable oils.
Trans fats are found in highly processed and packaged foods. Think junk food, fried food, commercial baked goods, margarine.
They have been shown to have the following negative health effects: increase inflammation, reduce “good” HDL cholesterol, increased “bad” LDL cholesterol and triglycerides, and increase risk of heart disease and diabetes.
How Much Fat Should You Eat?
The dietary reference intake (DRI) for adults is 20-35% of total calories from fat.
The AHA recommends that majority of dietary fats should come from monounsaturated and polyunsaturated fats, and that these fats should be eaten in the place of saturated and trans fats. They recommend aiming for no more than 5-6% of daily calories coming from saturated fats.
Best Sources of Dietary Fat
- high-quality animal meat/fat (ideally grass-fed, not grain-fed)
- fish, seafood
- olive oil
- coconut oil
Fat is an essential macronutrient made up of fatty acids. Fat is important for energy provision, energy storage, satiation, metabolism, vitamin absorption, hormone function, and many other functions within the body. Different types of fat include saturated fat and unsaturated fat (monounsaturated and polyunsaturated). The best sources of dietary fat include high-quality animal meat/fat, fish and seafood, eggs, nuts, seeds, avocado, olives, olive oil, and coconut oil.
That wraps up this article on fat – the final macronutrient in this macronutrient series!
I hope you found these articles interesting and helpful, and that they helped clear up any confusion or misconceptions surrounding macronutrients. If you enjoyed this article on fat, or this macronutrient series, let me know in the comments below!