Dietary Fats: The Complete Guide

Dietary fats have yet again been brought into the public eye with the National Obesity Forum (NOF) reporting that people should eat more fat, eat fewer carbohydrates and stop counting calories. This has received a wide scale backlash from many health and fitness experts and academics as irresponsible and even dangerous. Before we start on our journey into fat I would like to make my position clear on the whole thing, fats are not ‘bad’, carbohydrates are not ‘bad’ and the big issue I have with the whole thing is stating that people should not worry about their calorie consumption!


Regardless of where your calories come from, if you eat more calories than you expend then you will gain weight; this is the simple law of the universe and cannot be avoided! Does this mean that some people shouldn’t eat more fat? Of course not, as we will discover fats play an important role in health, in fact not just important essential. Does this mean that we should eat more fat and less carbs? Well it depends on your goals, as a guideline protein and fats are essential in the diet and the amounts included should reflect the basic needs of a person, with carbohydrate being used to provide energy and fibre to make up a remainder of the calories you need to reach your allotted amount of calories for the day. Obviously if you prefer more fat in the diet (let’s say you are a nut butter addict) then have more fats, if you enjoy carbs then keep fats at a moderate level and increase your calories from carbs and hit your protein allowances. It really is that simple and this is the advice in my opinion the media should be portraying instead of promoting crash diets and the constant flip flopping between carbs are good fats are bad, fats are good carbs are bad nonsense that has been going on for what now feels like forever.


For most people that is all the information they need and would, if taken on board, be enough to lead happy, healthier, non-obese lives with less concern for metabolic disorders such as heart disease, diabetes and reduce the risk of certain cancers. Once this message is put across then we can worry about the details of fat types, carbohydrate types and protein requirements for their goals.

Even when we look at fat there seems to be a constant change of opinion on the types of fat we should eat in the diet. Saturated fats have always been seen as unhealthy and unsaturated fats as healthy, eating cholesterol is bad for you one minute and not the next. So what is the truth in the matter?

Firstly let’s take a little look at what the different kind of fats are and the roles that they play in the body and where some of the conflicting information comes from. Aside from their role in energy production and storage of excess energy intake fats are essential because they contain several important vitamins such as A, D, E and K. Dietary fats, once digested and absorbed are also used to make key components of cells including the phospholipid membranes as well as playing a role in digestion, being used to create bile acids and of importance for those who train regularly are an essential component in steroid hormone formation. Insufficient dietary fat intake has been associated with disruption of our hormonal systems which can have knock on effect on both physical and psychological wellbeing.


Certain fatty acids are also important cellular signallers (called icosanoids) that drive many of the body’s functions. These ‘chemical messengers’ are derived from both omega-3 (O3) and omega-6 (O6). O6 icosanoids are more likely to be pro-inflammatory so have got a lot of bad press for this reason, but as with most physiological processes there is always two sides to the story. Remember O6 fatty acids are essential for a reason and that is because inflammation is not always a bad thing (think about an injury, without inflammation the recovery process would never get started and this would not be a good thing!), what we don’t want is dietary induced long term inflammation. This long term inflammation and chronic health issues associated with inflammation have been blamed on excessive O6 and saturated fatty acid intake, with recommendations to either reduce sources of O6 or to increase the amount of O3 in the diet to create a more favourable ratio to reduce inflammation, and of course to reduce saturated fatty acid intake.. but we will get back to this later.


So what is the difference between a saturated and unsaturated fatty acid? Well dietary fats are known as triacylglycerols (TAG) and contain three fatty acid chains attached to a glycerol backbone. The roles that fatty acids play in the body is dependent on their structure and is related to the length of the fatty acid chain, the number of connected carbons, the level of unsaturation and the position of the double carbon bond.. so our O3 polyunsaturated fatty acid has a double (C=C) bond three places from the Omega Enda of the chain. The omega end is the methyl group (CH3 end) and is considered to be the far end of the chain, the alpha end is the carboxyl group (COOH end) which combine to form the glycerol backbone… Still with me?


Those that contain a single C=C double bond are monounsaturated fatty acids (MUFA) and those (like O3 and O6) that contain multiple C=C bonds are polyunsaturated fatty acids (PUFA). Fatty acid chains that have no double carbon bonds are, you guessed it, saturated fatty acids. The wide spectrum of physiological roles the different fatty acids play in the body are still to a certain extent poorly understood. To reiterate, of all the fatty acids O3 and O6 are essential meaning that they need to be found in the diet. The ‘parent’ fatty acid of the O6 family of fatty acids is linoleic acid (LA) and the parent fatty acid of the O3 family is alpha-linolenic acid (ALA). As with amino acids, some fatty acids are considered conditionally essential (meaning they are required in greater amounts under certain conditions such as during growth and illness) these include two of the family of O3 fatty acids Eicosapentaenoic Acid (EPA) and Docosahexaenoic Acid (DHA).


The body being as clever as it is can create monounsaturated fatty acids from the carbon contained in carbohydrates and proteins. Unfortunately it is not as clever as we would like as we do not appear to have the enzymes to insert a double bond at the n=6 or the n=3 position, hence why they are essential in the diet as the body cannot create them! The amounts and ratios of O3 and O6 in the diet can influence cell membrane properties such as fluidity, flexibility, permeability and the activity of enzymes within the cell membrane which has the potential to impact on exercise recovery, mental state and performance and have even been implicated in pathways that promote muscle building. O3 and O6 fatty acids may influence gene expression which directs a whole spectrum of physiological processes such as metabolism, immune function and inflammation and the manufacture of important steroid hormones.


I think at this point we have discovered that our unsaturated fatty acids have a generally positive effect on the body, especially O3 with O6 being essential but needing a balanced intake. It is saturated fatty acids that appear to play most of its roles through energy provision and it is unsurprising that in those with metabolic disorders, especially associated with obesity, that saturated fat content is high. The problem with these types of studies is that controlling for lifestyle factors including exercise and being of a normal weight can skew the results, meaning that when you focus on a single outcome (saturated fat intake for example) the nuance of the findings in terms of the bigger picture can often be lost.. it is true that saturated fat intake has been associated with obesity and other health conditions, but the same is also true of high sugar and carbohydrate intake and basically high anything intake.. even protein. This is where a lot of the confusion about carbs and fats comes from. These studies do show an association, but unless we can get a bigger picture as to why then they should always be treated with caution when applying dietary advice. So the question is are saturated fats bad for you, or are they bad for you in the context of an inactive lifestyle with an overconsumption of foods?


From the roles they play in the body it is wise to suggest that you consume enough MUFA and PUFA to provide for the essential roles they play within your daily fat intake, but that does not mean that saturated fats should be avoided entirely as long as we don’t have excessive amounts. Debates still rage about the effects of saturated fat on health including risks of cancers and cardiovascular disease. One key marker of cardiovascular disease are cholesterol levels, it appears that if we replace saturated fats in the diet with unsaturated sources we get a lowering of cholesterol which may be beneficial for long term cardiovascular health. Saturated fatty acids have been shown to be a key dietary factor for increasing cholesterol, which is why it has been government policy to suggest a reduction of saturated fats in the diet, as you can see this is in conflict with the NOF! No wonder people are confused. The inclusion of saturated fatty acids in the diet in small amounts should be considered for the roles it plays in steroid hormone formation (which comes from cholesterol), cell membrane regulation and in nerve transmission, immune function and general energy provision.


We should always consider the amount of saturated fat in the diet before deciding to reduce it. As a general guideline if we are you are consuming less than 30% of your fat calories from saturated sources and not eating an excessive amount of calories, then there should be no need for concern. If you’re eating plenty of lean meats, fish and the occasional bit of dairy and red meat then saturated fat intake is not really worth a second though. However lots of take-outs a week, eating lots of cakes, pastries and tons of highly saturated fatty animal products might get you in some bother, but again are saturated fats to blame or is it the lack of balanced nutrition, too many calories and increased weight gain?


One of the biggest areas of confusion with fats is the consumption of a type of fat called cholesterol. Cholesterol is actually a lipid molecule that plays important roles in cell membrane construction and function and acts as a precursor to steroid hormones, bile acids and vitamin D so it is certainly not to be considered bad and it will be synthesised in the body if not enough is present in the diet. You may have heard of people talking about good cholesterol and bad cholesterol. Good cholesterol is commonly referred to as HDL cholesterol with LDL being bad. HDL stands for high-density lipoprotein and LDL low-density lipoprotein; these are specialised fat carriers that allow it to be transported in the blood, the type of carrier (HDL or LDL) has an influence on our health and fat intake can influence the amount of HDL to LDL we produce.


LDL is considered ‘bad’ as if present in large amounts in the blood these are taken up by a specialised type of white blood cell called a macrophage, these then become enlarged and produce something called a ‘foam cell’ which can become trapped in the walls of blood vessels and contribute to plaque formation and thickening of the arteries. These plaque formations are one of the main causes of cardiovascular illnesses including strokes and heart attacks.

More importantly than the amount of LDL present in the blood it is the ratio of LDL to HDL that is important to health not necessarily the amount. The higher LDL to HDL ratio being an indicator of cardiovascular risk, this risk can be calculated by taking the total amount of cholesterol and dividing it by the amount of HDL present. A ratio of over 5 indicates an average risk of heart disease, the risk for heart disease doubles if there is a ratio of around 9.5 and someone with a cholesterol ratio of 3.4 has approximately half the average risk for heart disease. LDL levels can also be influenced by a variety of dietary factors, as you would expect these include high saturated fatty acid intake, dietary cholesterol, fibre and alcohol consumption.


More recent studies are starting to show that specific types of saturated fatty acids may have different impacts on cholesterol, with palmitic acid and myristic acid increasing cholesterol levels, whereas stearic acid has little of no impact. It also appears that PUFA can cause increases and decreases in LDL depending on the source.. as if this wasn’t confusing enough. MUFA and O6 have significantly reduce LDL levels in the blood when they replace saturated fatty acids in the diet. It appears O3 fatty acids can have a dose dependant effect on LDL levels, with around 1g per day having positive effects on LDL levels, however higher amounts of over 3g have been shown to increase LDL.


I think at this point we need to stop for a second a take a step back and think ‘bigger picture’. It is easy to get caught up in the minutiae of what is going on in the body and get confused. I think a good view on this is to see that many of the things we talk about can be good or bad for the body depending on the amount we consume. If we stop zooming in on the detail for a second (which from my perspective is interesting from an educational point of view), I can see how some of this information may have muddied the waters further. So stop, take a deep breath and go back to the initial point I made right at the start about keeping it simple; Do some exercise, eat the right amount of calories, limit the amount of junk you eat, eat enough protein and fat and fuel your training with fibrous carbs and a bit of fruit and veg and your health will for the most part take care of its self.

For more information on fats check out or video on the CSN you tube channel..


Right, back to the science stuff.. Interestingly studies on dietary intake of cholesterol have demonstrated mixed effects on LDL levels and this may be due to genetics, the total amount of fat included in the diet and other dietary factors, not the amount of cholesterol within itself. Dietary cholesterol intake has a slight association with blood cholesterol levels, as around half of the cholesterol found in the blood is actually created within the liver from other fatty acids. This is highlighted by the fact that the average person consumes around 0.3g of cholesterol a day and create but the body 1g to maintain normal function. If dietary cholesterol is increased then the liver production decreases and it is theorised that an individual’s response to consuming dietary cholesterol, in terms of LDL levels, is dependent on their ability to appropriately adjust levels of synthesis in the liver and this may be linked to obesity due to disruptions in cholesterol metabolism. This means for most people it unlikely that cholesterol consumption would be of concern unless they had a genetic/hereditary concern about their heart health.


One thing I can be very clear on with regard to fat intake is avoiding as far as possible the Frankenstein’s Monster of the fat world... trans-fatty acids. These are found in small amounts in meat and dairy products and are not generally a concern. However, they were developed and are widely used in commercial cooking as they keep for longer and can be reused. Trans-fatty acids have the awful effect of simultaneously increasing LDL and reducing HDL. This is obviously not great for the body especially if you are unknowingly consuming a lot of it! They are often present in hydrogenated oils and margarines and because of their commercial use it’s not just the calorie content of your take out or cake you need to consider, it is how much trans-fatty acids as well. If you tend to use a lot or margarine or reusable oils in your own cooking baking then it is worth checking to see if it contains Trans-fats which are often labelled as hydrogenated fats and oils.


It’s ok we’re nearly there, just a few final thoughts and recommendations. The study of how dietary fats affect physiological processes is still an area in which much is to be learned. As the understanding of fatty acids and the roles they play increases, recommendations on intake have also shifted with previous associations with health issues being revised and reformed on a regular basis which adds to the nation’s confusion. Fat intake is suggested to be around 1g/kg of lean body mass per day, but defining a maximum is really an individual thing and depends on your goals, overall calorie intake and most importantly what foods you enjoy eating and this should guide your eating habits (wthin reaason of course!) and as long as you are consuming enough nutrient dense foods to support health then 'sweating the small stuff' should be less of a concern.


Thanks for reading,

Dr P.

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