The Nutrition Series: Fat 101

Fats: The Misunderstood Ally

Fats have been demonized in the nutrition space historically however, they have such a critical role in the human body that it is fundamentally negligent to refrain from consumption. Truly, dietary fats have undergone such a massive pendulum swing in terms of recommendations and the way they are viewed in the modern diet. It is no wonder that such confusion exists today. What’s the difference between saturated, monounsaturated and polyunsaturated fat? What’s up with trans fats? We’ll explore all of these questions and more alongside the current recommended guidelines and various sources of fats for structuring your diet.

What is Fat?

There are, for the sake of argument, three types of dietary fats including triglycerides, phospholipids and sterols. Most dietary fats are triglycerides and are made up of glycerol and three fatty acid molecules joined together. Our body produces most of the fat we require however, some fats are considered essential and must be obtained through diet alone. Much like essential amino acids, omega-3 and omega-6 fatty acids are essential and obtained through exogenous sources only.

There are also different types of fats in terms of structure. For example, there are saturated fats, unsaturated fats (mono, poly etc.),  and trans fats. Fatty acids can also be found in different chain lengths, which have wildly different implications for an individual’s health. We’ll break this out in more detail but for now, be aware of the various types of fats that exist.

Much like the other macronutrients, there are of course, various sources dietary fats. Fats can be obtained through the diet from both animal sources and plant sources. In addition, there are also trans fats, which are typically produced through industrial processes, and are a poor choice for inclusion in your diet, as will be shown.

Types of Fats

A discussion on dietary fats must begin with a thorough explanation of the types of fats that exist. Indeed, fat isn’t just fat, there are saturated fats, unsaturated fats and trans fats. Each has a uniqueness to its molecular structure that produces surprising consequences for the seemingly insignificance of the difference.

Saturated Fats

Saturated fats are saturated with hydrogen molecules and have single bonds between each carbon atom. This allows for the molecules to be stacked together tightly and thus, are more solid at room temperature (think butter and coconut oil).

Unsaturated Fats

Unsaturated fats contain one or more double bonds between carbon atoms (in place of a hydrogen atom). This creates kinks or bends in the chain of the molecule and thus, molecules cannot pack tightly together. Unsaturated fats are, therefore, liquid at room temperatures and common examples include plant oils such as olive oil and canola oil. Unsaturated fats can also be obtained through various seeds, nuts and fish.

Trans Fats

Trans fats have a similar structure to unsaturated fatty acids however, hydrogen atoms have been added to the molecule thus replacing some double bonds with single bonds. This makes the structure more linear and resemblant of saturated fats.

These types of fats are produced by heating liquid vegetable oils in the presence of hydrogen gas and a catalyst, a process called hydrogenation. Trans fats can also be found naturally in beef and dairy fat in minute quantities.

Omega-3 and Omega-6

Omega-3 and 6 are polyunsaturated fats that are considered essential as, you guessed it, the body doesn’t produce them naturally (dang you catch on quick).  The “3” and “6” notations refer to the last double bond in the molecular structure. In omega-3 fatty acids, the last double bond occurs 3 carbon atoms away from the omega (tail end of the structure) and in omega-6…. well, 6 carbon atoms away.

Of course, there are different types and different sources of omega-3s and 6s. Some common types of omega-3s include Eicosapentaenoic acid (EPA), Docosahexaenoic acid (DHA) and Alpha-linolenic acid (ALA). The most common omega-6 fatty acid is linoleic acid, which the body can convert to arachidonic acid (AA). Omega-3s are typically considered to have more health benefits (which will dive into shortly), while omega-6s are mostly utilized for energy (with some degree of evidence of anti-inflammatory properties).

Role in the Body

The lower the fat, the healthier the food, right? That is likely the proclamation you’ve been fed for much of your adult life. Misconceptions around fat have been long-held and widespread. Dietary fats are, indeed, not only beneficial to your health but vital for optimal health. Fats are utilized for numerous processes in the body including a source of energy, hormonal signalling, insulation (protection) and digestion.

Taking in more energy (calories) then what is required to support the body and offset losses of calories burned through activity, the body stores this excess energy as fat. While the stubborn fat around your midsections may be a source of frustration, in the light of evolutionary biology, its historically served as a source of energy during periods of food scarcity. While glycogen may provide a source of immediate energy, our ability to store glycogen is limited. Our ability to store fat, on the other hand, has very few limitations.

Energy Source

Quite positively, fat is a prime source of energy. Containing almost double the amount of energy compared to a gram of carbohydrate, fats serve as a pool of energy that can be drawn upon to meet our energy demands from our activities throughout the day (both exercise and non-exercise physical activities). This was highly advantageous for our ancestors, who could store excess energy as fat during periods of food abundance, to prepare for periods of near starvation. This of course, is not as advantageous in modern society where there are literally thousands of calories awaiting your consumption just 10ft away from your couch. Thus, while dietary fat can serve as an important source of energy, it's crucial to regulate intake to avoid unwanted weight gain.

Chemical Signalling

Importantly, dietary fat is necessary for producing a wide range of chemical signalling molecules within the body which serve vital functions. Firstly, dietary fats are essential for producing hormones including steroid hormones such as testosterone, estrogen and cortisol. Without adequate intake of dietary fats, hormonal imbalances can occur and thus, dysregulated bodily functioning.

Fats also serve as precursors to other signalling molecules including the lipid-based eicosanoids, which include prostaglandins, thromboxanes and leukotrienes. These molecules are vital in immune response, inflammation, blood clotting and additional physiological processes. Dietary fats assist in transport and absorption of fat-soluble vitamins including vitamins A, D, E and K. Without adequate dietary fats, these vitamins are not absorbed as readily, which may compromise additional physiological pathways and upset homeostasis.

Cellular Membranes and Body Composition

In case you forgot basic human biology, fats are integral to the structure of cellular membranes, the fundamental component being the phospholipid bilayer. Dietary fats utilized as the building blocks of cellular membranes and intake of dietary fats may influence the cellular membrane in crucial ways. Firstly, current consensus in nutrition science hold that the balance of saturated fats to unsaturated fats may influence the fluidity of membranes.

Specifically, increased intake of saturated fats may lead to increased rigidity in membranes versus unsaturated fats, particularly omega-3s, may lead to increased fluidity. This is not necessarily good, nor bad, the key here is balance. Membrane fluidity is a spectrum and the extremes on either end are not desirable.

Fat, unsurprisingly, also plays a role in insulation and protection (we’re not talking about extra insulation around your gut here). Vital organs are surrounded by adipose tissue, which aids in protection and temperature regulation. Furthermore, some degree of adipose tissue in the subcutaneous layer of the skin is desirable again for thermoregulatory effects and protection from the external environment.

Health Implications

Heart Health

Dietary fat and heart health have had a challenging history. In the 1950s, the so-called “diet-heart” hypothesis was introduced, which essentially claimed that saturated fat increased the risk of cardiovascular disease. Despite being based on weak, associational evidence and several repeated (and failed) studies aimed at substantiating these claims, this idea persisted. That is, up until a decade ago when there began renewed interest in examining these potential causal links. Since then, there have been over 20 peer-reviewed studies all determining that there is in fact no link between dietary saturated fat and the development of cardiovascular disease(1).

Current stances on the intake of saturated fat suggest that eating too much saturated fat can increase low-density lipoproteins (LDL) “bad” cholesterol. Conversely, consuming monounsaturated and polyunsaturated fats helps to raise high-density lipoproteins (HDL) “good” cholesterol. This notion, however, is being highly scrutinized in present nutritional science. For the purposes of this discussion, I shall avoid delving into the nuances and focus mainly on what is currently agreed upon. That being, increasing monounsaturated and polyunsaturated fats (to appropriate levels) can assist in lowering high blood pressure and reduce the potential for plaque build up within the arteries. Trans fats, on the other hand, do raise LDL and lower HDL and have been consistently implicated in the development of heart disease. It would be prudent to avoid trans fats as part of your healthy approach to dieting.

Brain and Nerve Health

Consuming healthy dietary fats can also affect the brain. Aside from lowering blood pressure (a risk factor for Alzheimer’s disease), consuming dietary fat can help regulate synaptic transmission, membrane fluidity and signal-transduction pathways. Particularly, the polyunsaturated fats omega-3s and omega-6s have been implicated in brain health with the focus on consuming more omega-3s. Diets low in omega-3s have been associated with neuropsychiatric and neurological disorders with inflammatory outcomes(2).

Skin, Hair and Bone Health

Adequate intake of dietary fats also has some surprising implications in skin, hair and even bone health. Consumption of appropriate dietary fats can assist the appearance of skin and hair through a number of various pathways the worthiest of highlighting being the anti-inflammatory effects of healthy dietary fat. Reducing inflammation in the skin helps fight inflammatory based conditions such as acne, psoriasis and rosacea. Similarly, reducing inflammation in hair follicles helps to produce thick and moist strands of hair improving the overall appearance of your hair. There are also essential vitamins associated with skin and hair health (vitamins A, D, E and K) that see improved absorption with appropriate intake of healthy dietary fats.

Bone health can also be improved through healthy dietary fat intake. Most notably, anti-inflammatory properties of healthy dietary fats can help fight bone loss and osteoporosis, which are exacerbated by chronic inflammation. Bone health also benefits from improved vitamin absorption and hormone production both of which, as we’ve seen, can be regulated through adequate intake of dietary fat.

While this is a short (and highly summarized) list of the many benefits that consuming dietary fats can bring, it is crucial to highlight that dietary fat shouldn’t be demonized as has been done historically.  

Whole Food Sources

There is a plethora of sources of each of the types of dietary fats and incorporating several is a key component of a healthy approach to dieting.

Monosaturated Fats

Monosaturated fats are typically found in seeds and nuts and the associated oils. Typical sources of this type of fat include the following:

·        Olive oil

·        Avocados

·        Nuts (i.e., almonds, peanuts, cashews)

·        Seeds (i.e., pumpkin seeds, sesame seeds)

Polyunsaturated Fats

Polyunsaturated fats can be found both in animal and plant sources. Some common sources include:

·        Fatty fish (i.e., salmon, mackerel, trout and sardines)

·        Flaxseeds and flaxseed oil

·        Chia seeds

·        Walnuts

·        Soybeans and soybean oil

·        Sunflower seeds and sunflower oil

·        Corn oil

Omega-3s

While omega-3s are a type of polyunsaturated fat, the implication of omega-3s in health make it particularly important to highlight separately. Rich sources of omega-3s include:

·        Fatty fish (i.e., salmon, mackerel, herring and tuna)

·        Flaxseed and flaxseed oil

·        Chia seeds

·        Walnuts

·        Hemp seeds

·        Algal oil (derived from algae, suitable for vegetarians and vegans)

·        Fish oil supplements (for those not consuming enough fatty fish)

Omega-6s

Similar to the above, it's worth highlighting omega-6 sources separately. Sources of omega-6s include:

·        Sunflower seeds and sunflower oil

·        Corn oil

·        Soybeans and soybean oil

·        Safflower oil

·        Pumpkin seeds

·        Pine nuts

Saturated Fats

Saturated fats are found in both plant and animal sources (mostly in animal sources). Sources of saturated fats include:

·        Fatty cuts of meat (i.e., beef, lamb and pork)

·        Cheese

·        Whole-milk and other full-fat dairy products

·        Butter

·        Chicken skin

·        Cheese

·        Coconut oil

·        Palm oil

Trans Fats

Lastly, I’ll touch on trans fats as more of an avoid this list approach. Trans fats are mostly found in processed foods, and intake should be minimized as much as possible due to their adverse health effects. Sources of trans fats in the diet include:

·        Margarine

·        Shortening

·        Partially hydrogenated oils (found in many processed and fried foods)

Incorporating a variety of these whole food sources into your diet can help ensure a balanced intake of different types of dietary fats, supporting overall health and well-being. Remember to prioritize healthy fats while minimizing intake of unhealthy trans fats. The above lists are not comprehensive lists however, they serve as a starting point for structuring diet.

Fat Supplementation

While most individuals can meet their dietary fat requirements through diet alone (surprise, surprise), there may be cases where supplementation can have added health benefits.

For example, supplementing with omega-3s, particularly EPA, can improve cardiovascular, brain and join health. Furthermore, additional intake of omega-3s can improve skin conditions and hair health.

As dietary fats have properties associated with improved vitamin absorption, those individuals with fat malabsorption disorders, digestive issues or those following low fat diets may see improvements by supplementing fat.

Finally, those following a plant-based diet may have insufficient omega-3 intake particularly in the case of EPA and DHA. These individuals can benefit from algae-based omega-3 supplementation to ensure adequate intake of these essential dietary fats.

As with any dietary recommendation, it is important to discuss it firstly with your physician before making any dietary changes targeting health.

Fat Requirements

There are varying recommendations from organizations when it comes to dietary fat consumption. Recommendations from the World Health Organization and Dietary Reference Intakes that an appropriate allocation of dietary fat in the diet is approximately 20 – 35% of calories. The low end of this spectrum would be to ensure adequate consumption of total energy, essential fatty acids and fat-soluble vitamins occurs. As stated previously, it is important to include a wide-variety of healthy sources within that range of caloric intake to ensure optimal health.

Fat is an often overlooked component of the diet. Historically, this crucial macronutrient has been demonized and misconceptions continue to persist. Luckily, nutrition research during the last few decades targeted at better understanding the essential roles that dietary fat plays in the diet continue to demonstrate that dietary fats are vital to optimal health. Furthermore, our continued understanding of the different types of dietary fats have allowed recommendations to evolve and become more focused for improving health at the individual level.

References

1.      Teicholz N. A short history of saturated fat: the making and unmaking of a scientific consensus. Curr Opin Endocrinol Diabetes Obes. 2023 Feb 1;30(1):65-71. doi: 10.1097/MED.0000000000000791. Epub 2022 Dec 8. PMID: 36477384; PMCID: PMC9794145.

2.      Chianese R, Coccurello R, Viggiano A, Scafuro M, Fiore M, Coppola G, Operto FF, Fasano S, Laye S, Pierantoni R, Meccariello R. Impact of Dietary Fats on Brain Functions. Curr Neuropharmacol. 2018;16(7):1059-1085. doi: 10.2174/1570159X15666171017102547. PMID: 29046155; PMCID: PMC6120115.