• Danielle Stephens

Facts on Fat

Updated: Jan 14, 2021

There’s always one nutrient that people want to focus on being the root of all our nutrition foes. Fat is definitely one of those. It has yo yo’d from being the worst of the worst, causing all different kinds of diseases such as obesity and heart disease, to being the nutrient that we should all be consuming lots of (aka the keto diet).

So, what should we all believe? Are fats really as bad as they are made out to be? How much fat and what fats should we be eating? Should we be cutting them all out or increasing our consumption?

In this blog post I will be talking all things fat, with evidence-based nutrition to understand what fats really are, why they are important and what we should be incorporating in our diet!

First up what are fats?

Fats are made up of a mixture of different fatty acids attached to a molecule known as glycerol. There are various different types of fatty acids which you may have come across before, these include, saturated and unsaturated fatty acids.

Fats are classed into either saturated or unsaturated based on the types of bonds that are present in their structure. Saturated fats contain no double bonds meaning that the fatty acid chains can pack nice and closely together, resulting in the fat being a solid at room temperature. Butter for example, is classed as a saturated fat.

On the other hand, unsaturated fatty acids contain a mixture of both single and double bonds. This means that there are slight kinks in the fatty acid chains so they can’t pack very tightly together. This results in the chain being more fluid. Unsaturated fats are usually liquid at room temperature, such as olive oil.

Unsaturated fats can be further sorted into different groups depending on how many of these double bonds are in their structure. Mono-unsaturated fats only have one double bond, whereas poly-unsaturated fats have two or more double bonds.

It is slightly more complicated than this though as fats are not solely made up of either all saturated fat or all unsaturated fat; they are comprised of a mixture of both.

Take butter for example, it is made up of approximately 63% saturated fat, 26% monounsaturated fat and 4% polyunsaturated fats. Butter is classed as a saturated fat as it contains the highest percentage of this type of fat. This is also the same for oils such as olive oil, which contains 73% monounsaturated fat, 10% polyunsaturated fats and 14% saturated fats.

Why do we need fat in our diet?

Fats are an essential source of energy. We can extract more energy from fat than we can from carbohydrate meaning it can fuel us for longer. This is why we use fat as a source of energy when we are doing endurance movement such as walking, jogging and cycling. Without fat our muscles would not be able to work!

Fats also make up extremely important components of our individual cells. Our cell membranes, the thing that keeps all our cell contents in one place, are made up of fats. Other important molecules that we use to send signals around the body are also made of fats. So, without fat we would not be able to function.

Fat tissue, also known as adipose tissue, is also used as a vital cushioning layer for our organs, such as our heart and kidneys. It stops our organs from getting damaged when we are moving around.

There are several vitamins that we must have in our diet which are known as fat-soluble vitamins. These include vitamin A, D, E and K. These vitamins are unable to be carried around in the blood as they do not like water, meaning we can only absorb them if they are attached to fats.

So, as we can see, fats are essential for our bodies to function, therefore we need to consume them in our diet.

How our body deals with fat

When we eat food that contains fat, the fats are broken down in our stomach and are absorbed into the blood stream. They are then transported to the liver where they are processed before being transported onto the adipose tissue (fat tissue) where they are stored ready for use. Some fat is also stored in the liver and the muscles.

Fat can also be made from other energy sources that we do not use straight away such as carbohydrates and protein. This is because we can only store a certain amount of carbohydrate (as glycogen) in our muscles and liver. This means when we have consumed enough carbohydrates to refill our glycogen stores, the remaining carbohydrates will be converted into fatty acids. This is also true for proteins. Protein is broken down and then used to replace and rebuild proteins. However, if we have already fulfilled this process, the remaining protein can be converted into fat, as we cannot store any protein. Our bodies are just very efficient at extracting every last bit of energy and wasting none!

So why all the negativity around fat?

It all started back in 1958 when The Seven Country Study was first initiated (1). This was a huge collaborative study which looked at food consumption in 16 groups from 7 countries, and cardiovascular disease risk factors. The strongest link which was observed was the intake of saturated fat and the risk of coronary heart disease – the higher the saturated fat intake, the higher the risk of developing coronary heart disease (2). And here the born the hate for fat was born.

This study also linked high saturated fat intake to high cholesterol levels. High cholesterol has been associated with health risks such as atherosclerosis, where fat deposits build up in our veins and may cause a blood clot, a stroke, or even a heart attack (3).

Despite the many published papers reporting the link between saturated fat intake and coronary heart disease there has also been recent evidence to suggest that this association may not be so simply explained. There are some populations that have relatively high levels of saturated fat in their diets, for example the French, however they have low incidence of coronary heart disease. This highlights the complexity of nutrition research and how hard it is to truly say that a disease is caused by one dietary factor - our diets are the sum of its components, so we need to focus on the diet as a whole, not only focus on one dietary component.

MYTH BUSTING: coconut oil. Many people assume coconut oil is the ‘healthiest’ oil, with many recipes nowadays opting to use this oil in cooking rather than the traditional choice of butter or olive oil. However, what you may not realise is that coconut oil is actually a saturated fat. It contains 82% saturated fat.

Chocolate brownies for example, are not ‘healthier’ by switching out the butter for coconut oil, it will merely give the brownies a more coconutty flavour, and is a good substitute for butter if you're vegan!

What’s the deal with unsaturated fats?

Unsaturated fats are normally referred to as being ‘good’ fats. This is because studies have been conducted that have shown that switching saturated fats in your diet to unsaturated fats, and therefore consuming higher amounts of unsaturated fats has health benefits (4,5).

There are also some specific fats that are described as being ’essential’. This is because we cannot make them in our body, therefore we need to get them from our diet. These fats are important as they are the ones that are mostly present in our cell membranes, in signalling molecules used for sending messages around the body and are needed for vision and brain function. It is clear that they are VERY important.

These essential fatty acids are known as polyunsaturated fats, which are also called omega 3 and omega 6 fatty acids. I’m sure you have all heard of these!

We can obtain omega 3 and omega 6 fatty acids from certain foods in our diet, for example omega 3 fatty acids are present in oily fish and omega 6 fatty acids are present in vegetable oils. These polyunsaturated fats have been associated with multiple health benefits due to the essential and protective roles they play in our body. Omega 3 fatty acids are required for normal vision, brain and heart function. Omega 6 fatty acids are essential for the maintenance of our skin, reproduction and immune functioning.

Increasing the consumption of these fats has also been shown to decrease the levels of fat that circulates in our blood stream and therefore decreases our risk of diseases, such as cardiovascular disease (6). There have also been many studies undertaken in animals looking at the cardioprotective effects of omega 3 fatty acids. These have concluded that high intakes of these fats decrease your risk of having cardiovascular disease and the health complications associated with it, such as strokes and heart attacks. However, there are still mixed results from human intervention trials using omega 3 supplements, such as fish oil, to decrease the risk of developing cardiovascular disease. This means that we need to conduct more long-term trials to see whether increasing our intake has any substantial health benefits (7).

What we do know however, is that as a population we are not consuming enough omega 3 fatty acids in our diet. We should therefore be aiming to eat a bit more of these polyunsaturated fatty acids. There is a list below of foods that contain omega 3 and omega 6 fatty acids, to help you to maybe incorporate some more of these in your diet.

Take away messages

  • Eating fat will not make us fat. Having fat in our diet is essential for normal body processes – don’t be afraid of it!

  • It’s the type of fat not how much fat! Swap some of the saturated fat in our diet for unsaturated fats. For example, instead of using butter for frying, switch to using a drizzle of olive oil.

  • Classing fats as either good or bad is not the most helpful way of viewing fat. Fats contain a mixture of both saturated and unsaturated fatty acids.

  • There are links between serious health conditions and saturated fats, but these may be more complicated than we think.

  • Omega 3 fatty acids have been associated with health benefits, however the results obtained so far from human intervention trials are mixed. So, there’s no need to rush off to get fish oil supplements just yet.

  • Increasing our consumption of omega 3 fats as this will enable us to get the required amount of omega 3 fatty acids into our diets. I have made a list of foods that contain higher amounts of omega 3 and omega 6 fatty acids.

The best thing we can do is be aware of the health conditions associated with eating too much saturated fat. But don’t be afraid of having butter on your toast – food is there to be enjoyed, not feared.

BEWARE: foods that say they contain 0% fat such as yogurts usually contain much more sugar in order to make them taste as yummy. So sometimes it’s best to just opt for the full fat version.

Remember that diets don’t just consist of one component, they are the sum of all their parts. This means that we should not be focusing on one single nutrient in our diet, but we should think of our diet as a whole. Let’s not demonise one nutrient, lets focus on consuming more foods such as fruit and vegetables and wholegrains rather than solely thinking of what we should be cutting out. Diets should be inclusive not restrictive!

AND above all let’s remember to EAT HAPPY and LIVE WELL.




  1. The Seven Countries Study.

  2. Keys A, Menotti A, Karvonen MJ, Aravanis C, Blackburn H, Buzina R, et al. The diet and 15-year death rate in the seven countries study. Am J Epidemiol. 1986;124(6):903-15.

  3. Kromhout D, Menotti A, Bloemberg B, Aravanis C, Blackburn H, Buzina R, et al. Dietary Saturated and transFatty Acids and Cholesterol and 25-Year Mortality from Coronary Heart Disease: The Seven Countries Study. Preventive Medicine. 1995;24(3):308-15.

  4. Mozaffarian D, Micha R, Wallace S. Effects on Coronary Heart Disease of Increasing Polyunsaturated Fat in Place of Saturated Fat: A Systematic Review and Meta-Analysis of Randomized Controlled Trials. PLOS Medicine. 2010;7(3):e1000252., 2010

  5. Li Y, Hruby A, Bernstein AM, Ley SH, Wang DD, Chiuve SE, et al. Saturated Fats Compared With Unsaturated Fats and Sources of Carbohydrates in Relation to Risk of Coronary Heart Disease: A Prospective Cohort Study. Journal of the American College of Cardiology. 2015;66(14):1538-48.

  6. Skulas-Ray AC, Kris-Etherton PM, Harris WS, Vanden Heuvel JP, Wagner PR, West SG. Dose-response effects of omega-3 fatty acids on triglycerides, inflammation, and endothelial function in healthy persons with moderate hypertriglyceridemia. The American Journal of Clinical Nutrition. 2010;93(2):243-52.

  7. Abdelhamid A, Brown T, Brainard J, Biswas P, Thorpe G, Moore H, et al. Omega-3 fatty acids for the primary and secondary prevention of cardiovascular disease. Cochrane Database of Systematic Reviews 2020. 2020(3).

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