The Ultimate Guide to Simplifying Diet: Part 3 – Dietary Fat


Dietary fat has been the most vilified, and vaunted, of macronutrients – billed as either the sole cause of heart disease, or as a nutritional panacea requiring us to smother everything in butter, coffee included.

When it comes to you, chances are that more than any aspect of your diet, this part has you really, really confused.

In Part 3 to this series, we’ll break down:

  • the importance of fat
  • clarify some of the issues regarding saturated fats
  • discuss the importance of polyunsaturated fats i.e. essential fats
  • discuss where monounsaturated fats fit i.e. the much revered Mediterranean diet
  • discuss considerations for having a higher, or lower, dietary fat intake

The Importance of Dietary Fat

Dietary fat plays a number of important and critical roles in the body, including:

  • Energy storage – fat in the diet is primarily in the form of triglycerides (meaning three fatty acids bound to a glycerol, or sugar, backbone). The body can store excess energy from fat directly into fat tissue, or can convert excess energy from carbohydrates into triglycerides, to be stored in fat tissue.
  • Energy production – triglycerides can be broken down and released into circulation to be used (or in common parlance, burned) as energy. Fat oxidation is the primary energy producing route in aerobic conditions.
  • Vitamin absorption – the vitamins A, D, E and K are all fat-soluble, and we absolutely require a minimum of 7% fat in the diet to effectively absorb these vitamins. Collectively, these vitamins are important for vision (vit A), as the major fat-soluble antioxidant (vit E), for bone health (vits D and K), for calcium and phosphorous absorption (vit D), and for protection of arteries from calcification (vit K). That’s just a taster of how important the fat-soluble vitamins are – they are critical to optimal health.
  • Eicosanoid action – eicosanoids are often described as ‘local’ hormones. Their expression is under the influence of essential fatty acids stored in cell membranes, which are released to regulate important physiological processes like inflammation and blood clotting.
  • Hormonal function – reproductive hormones like testosterone and oestrogen require dietary fat intake, in particular cholesterol, for synthesis. Cholesterol is also vital to bile acid production, which helps metabolise fats (and eliminate circulating cholesterol), and is required for conversion of vitamin D.

These are just a few examples, from which you can plainly see one inescapable fat – dietary fat is crucial to human health.

The subject has, however, become convoluted – and the aim of this series is to simplify diet. Let’s break down your fat intake now, clearing up some mess along the way.

Saturated Fat – The Controversial One

The desired public health outcome underlying the recommendation to keep saturated fats to 10% of total calories, is a reduction in heart disease, which remain a leading cause of mortality in Western countries.

This is based on the effect that saturated fats have on some of the risk factors for adverse coronary outcomes – in particular, total cholesterol (TC) and LDL cholesterol, elevated levels of which are considered the primary risk factors for heart disease.

But using these risk factors may be too simplistic. Saturated fats raise total and LDL cholesterol, but they also raise HDL cholesterol. So it depends on what outcome or endpoint is used; using TC and LDL as primary endpoints will strongly implicate saturated fats. The marker, however, that is considered the most accurate predicator of heart disease is the ratio of TC:HDL – and using this marker, we can see a more nuanced picture – that the risk of heart disease depends on the what nutrient replaces saturated fat, and the overall composition of the diet.

This is why in looking at “hard outcomes”, i.e. deaths from heart disease, the pooled evidence of an association between saturated fat and heart disease is weak – but caution here, this may be because saturated fats were looked at as the sole dietary causative agent behind heart disease, when we now understand the role of other important dietary factors, including polyunsaturated fat intake, fibre intake, and food source.

This may prove to be an example of one of the biggest difficulties with nutrition science – that people eat foods, not nutrients in isolation. And when looking at foods, not simply the nutrient, there is evidence of health benefits from foods that contain saturated fats; full-fat dairy products are associated with lower risk of cardiovascular disease and obesity, and dark chocolate can reduce blood pressure.

Ultimately, it appears that the entire body of up-to-date evidence points to the same thing: that the replacement nutrient is a vital determinant of cardiovascular disease riskTo give you a synopsis:

  • decreases in heart disease risk from reducing saturated fat consumption are only observed where polyunsaturated fats, not monounsaturated fats or carbohydrate, replace saturated fats;
  • the seemingly neutral effect of carbohydrates is misleading: if refined carbs replace saturated fats, then heart disease risk increases; if wholegrain, high fibre, low glycemic carbs replace saturated fats, risk decreases;
  • the findings in relation to monounsaturated fats can also be misleading: many of the studies looking at monounsaturated fats were looking at monounsaturated fats primarily derived from animal fat and processed foods, and trans fats were included in the definition of monounsaturated fats in some study populations;

Simple Take Home Point: eating saturated fat as a by-product of your animal produce intake (like dairy or meat) is not a problem as long as you don’t overdo it (no, Bulletproof Coffee, no), keep your polyunsaturated fat intake balanced (eat more fish), don’t eat processed foods (no trans fats or excess omega-6’s) and eat high fibre, low GI carbs (lots of veg, some fruit, some starch). 

Polyunsaturated Fats – The ‘Essentials’

Polyunsaturated fats encompass the omega-3 and omega-6 fatty acids, which are the essential fatty acids i.e. we cannot live without a dietary source of these fats.

In Part 2, I talked about the importance of these fats as foundation nutrients to ensure are present in the diet. We looked at the balance of omega-3 to omega-6 as an important variable in human health, with excess omega-6’s found in processed foods and vegetable oils contributing to low-grade systemic inflammation that is observed in nearly every modern disease.

On the other hand, we have looked at the health benefits of the marine omega-3 fatty acids, EPA and DHA, in both inflammation and brain health, and of the absolute requirement for DHA for infant brain growth and cognitive development.

However, polyunsaturated fats, particularly DHA, improve cholesterol profiles by suppressing genes that increase cholesterol synthesis.

NB: recall that we only need relatively small amounts of omega-3’s. The population average at which cardio and cognitive benefits are seen is only 1g/day, and even in specific inflammatory conditions like rheumatoid arthritis, the benefits are seen with an average of 2.7-3g/day. In contrast, a teaspoon of butter would contain 4g fat, of which 2.6g is saturated and 1g monounsaturated. This is why some of the movements calling for excessive intake of saturated fats have it wrong; polyunsaturated fats exert a cardio-protective effect, but the proportion of polyunsaturated fats to saturated fats is important (see below). So proportionally, while we need smaller amounts of omega-3’s, it makes zero sense to excessively elevate saturated fats to a disproportionate level in ratio to polyunsaturates, based on overwhelming evidence from cohort studies and multiple randomized controlled trials.  

More specifically, for every 5% (as a proportion of energy) increase of polyunsaturated fats replacing saturated fats, there is a 10% reduction in risk of heart disease.

Thus, there is another ratio which appears to be relevant for human health: the ratio of saturated fat to polyunsaturated fat, which may be more important than total dietary fat intake for cardiovascular disease risk. Where the ratio of polyunsaturated to saturated fat is >1:1, heart disease risk decreases even in the context of a higher fat diet with 35-45% energy from fat.

Simple Take Home Point: it may be that absence of seafood/marine omega-3’s, not presence of saturated fat per se, is the real issue in terms of fat and heart disease. As per the recommendations in Part 2 – eat more oily fish (3-4 times per week), or supplement with fish oils if averse to fish, or supplement with algae oil if plant-based, and minimise processed foods to balance omega-6’s. If saturated fats are coming as a by-product of your animal produce intake, and you’re not overdoing the butter thing, then your ratio of poly to saturated fats will be good. 

Monounsaturated Fats – The Mediterranean Magic

Other than fish oils, monounsaturated fats are the most likely to be referred to by that moniker of “good fats.”

Monounsaturated fats are the type of fats primarily associated with the Mediterranean diet pattern – olive oil, nuts and avocados. Adding these plant-based monounsaturated fats can promote heart health, particularly in the context of a diet that is also high in fish and legumes.

Like the ratio of polyunsaturated to saturated fats, a high monounsaturated fat intake (through an average of 2 tablespoons extra virgin olive oil and one ounce of mixed walnuts, hazelnuts and almonds per day) increases HDL “good” cholesterol and decreases LDL “bad” cholesterol, even with a higher fat (41% energy) diet overall.

Simple Take Home Point: Add plant-based monounsaturated fats to your diet – consistently include 1-2 tablespoons of extra virgin olive oil or an ounce of nuts (or both). Avocados are in too. Eating fish and having a high fibre intake as your baseline will help to keep your ticker tip top. 

Fat Recap

Ok, I realise the theme of this series is simplicity, and we did cover some technical ground there – reiterating the question underlying this series:

What do I eat to lose/maintain a weight I’m happy with, and achieve optimal health?

Here is a recap on your fat balance:

Saturated Fats:

  • If you eat animal produce: then your saturated fat intake will be covered as a by-product of your meat and dairy intake. You could add moderate amounts of butter, coconut oil and dark chocolate for other health reasons (short-chain fatty acids, anti-microbial, fat soluble vitamins, antioxidants, blood pressure etc.). 
  • If you are plant-based: then it depends on your degree of plant-basedness (I think I just made that word up)

IF you eat eggs and dairy, then, well, eat eggs and dairy. You’ll get the short-chain saturated fatty acids in dairy fat, fat soluble vitamins in butter, and you’ll get vital cholesterol for your sex hormone and vitamin D synthesis from eggs. You can also add coconut oil and dark chocolate as per the recommendations below for fully plant-based eaters.

IF you are a fully fledged plant-based eater, then you’re likely ok for poly and monounsaturated fats (assuming you’re not eating a “vegan junk” diet). So emphasise additional saturated fats, particularly from coconut oil and dark chocolate. You’ll benefit from the energy producing effect of medium-chain fatty acids in coconut oil, as well as its fat burning, bacteria fighting, cognitive boosting effects. The dark chocolate will boost your antioxidants, help reduce blood pressure, and even improve your exercise performance

  • Bottom Line: if you eat animal produce, you don’t need to add much extra saturated fat; if you don’t, you should add saturated fat food sources, depending on what fits your way of eating.

Polyunsaturated Fats:

  • If you eat animal produce:  It’s clear that increasing polyunsaturated fats at the expense of saturated fats is beneficial, so in practical, food-based advise, this is simple – eat less fatty meat, eat more fatty fish. 
  • If you don’t eat fish and/or are plant-based: then supplement with a fish oil supplement or algae oil supplement, respectively.
  • Bottom Line: balance your omega-6:omega-3 ratio by reducing processed and packaged foods, and increasing marine omega-3’s from a direct source.

Monounsaturated Fats:

  • If you eat animal produce: add extra virgin olive oil, nuts and avocado to your weekly diet.
  • If you are plant-based: add extra virgin olive oil, nuts and avocado to your weekly diet.
  • Bottom LineEveryone can round out their dietary fat intake with olive oil, nuts and avocado.

Finale: Considerations for a Higher or Lower Fat Intake

This is where we’ll often hear broad prescription for how you should eat – as if everyone has the same needs. Bullshit: nothing in nutrition is one-size-fits-all.

At the end of the day, this is something that you should feel free to play around with – but remember one basic principle – carbs and fat are both energy nutrients, and they should be in an inverse relationship i.e. where one is higher, the other should be lower.

This is brief rundown of populations who may benefit from a higher or lower fat intake:

Higher Fat (Lower Carb) Diets:

  • People with epilepsyketogenic diets have been the gold standard for epilepsy since the 1930’s.
  • People battling cancer – I’m just putting it in here, it gets very emotional and many oncologists refuse to engage with the subject, but the literature is there and emerging strongly on ketogenic diets as an adjunct to chemo or radiation therapy.
  • People with obesity/overweight – low carb, high fat diets lead to greater weight loss in the short term
  • People who like to eat more fat – seriously, it doesn’t have to be related to health condition. Eat to your personal preference.

NB: If unrelated to a health condition, and your personal preference is for a higher fat (>40% energy) diet, then remember the essential pillars to make it optimal for your health – your omega-3 intake, a high fibre intake and added plant-based monounsaturated fats.

Lower Fat (Higher Carb) Diets:

  • Bodybuilders – preserving a higher carb intake, particularly while dieting to lose body fat, preserves lean body mass and prevents large decreases in strength.
  • Strength/power athletes – carbohydrate intake helps maximise hypertrophy, glycogen repletion and performance.
  • People with established heart disease – a low-fat, omega-3 enriched diet can help prevent heart attack.
  • People with obesity/overweight – see, everything works. The message here is that the goal with obesity and overweight is weight reduction per se, independent of the method. Low fat works, as low carb works, as balanced diets work
  • People who just like to eat more carbs – Again, what is your personal preference?

NB Summation: I am not a fan of excessively low-fat diets. It is too important a nutrient to restrict, and the reasons for doing so are not black and white (i.e. saturated fat and heart disease). Fat is vital to hormonal health, for men and women – but if men are guilty are overdoing fat, women tend to excessively restrict it. There is no need to drop fat to below 20% of your calorie intake (which, in my opinion, is the minimal threshold for a balanced diet and optimal health). Whether you go higher, or lower, the principles remain the same

  • balance omega-3:omega-6 – more fish/omega-3 supplement, less processed food
  • saturated fats come as a by-product of animal produce intake i.e. meats, whole-milk and milk products and/or add moderate amounts of butter, coconut oil, dark chocolate
  • keep polyunsaturated fat/omega-3’s proportional to saturated fats – substitute some meat for more white meat/fish/omega-3 supplement
  • add plant-based monounsaturated fats – olive oil, nuts, avocado

I hope this has helped keep a complex topic simple for you.

Next week, we’ll deal with carbs – another maligned and misunderstood nutrient.

Stay well.