The functions of lipids: Why fats matter more than you think

It's an unfortunate reality that the term 'fat' has been demonised in modern society. Whether it's being used as an insult or we're ruthlessly picking apart its presence on our bodies, it's safe to say it carries some negative connotations.

But, while it's true that carrying excess amounts of it can be detrimental, the fact is — we need fat. That goes for both on our bodies and in our diet. Essential amounts of body fat are crucial for insulating and protecting organs, supporting fertility and generally just keeping us alive [1]. Meanwhile, dietary fat plays an important role in giving us energy, aiding the absorption of vitamins and producing hormones [2].

Much of the importance of fat in the body comes down to a compound called 'lipids.' Sometimes referred to as essential fatty acids, these are crucial building blocks of human development. But what are lipids, exactly? And, how do you know the difference between 'good' fat and 'bad' fat? Read on to learn more about the functions of lipids — and how to incorporate them into your diet in a healthy way.

What are lipids?

If you Google "definition of lipids," you'll likely find plenty of science-heavy explanations, as the term is typically only used in medical literature. However, put simply, lipids are fatty compounds that help the body perform various functions [3]. Compounds are elements that create a chemical bond in the body, helping control what goes in and out of your cell membranes.

While all lipids look different depending on the type, they are typically fatty, waxy, or oily substances that are not soluble in water [4].

Types of lipids

There are three main types of essential lipids, and if you've ever had a cholesterol check, you might recognise some of the names.

Triglycerides

As the most commonly found lipid in the body and our diets, triglycerides make up more than 95% of the lipids in food. They're stored in the blood where they're turned into energy [5]. Or, if they're not used, this excess energy can be turned into fat cells for later storage.

Triglycerides tend to be solid when at room temperature (or colder), but runny and oily when melted. Think butter, lard and coconut oil.

Sterols

Sterols are organic compounds that are characterised by their biochemical makeup of four hydrocarbon rings [6]. If you think the term sounds similar to steroids, it's no coincidence. Sterols are a subgroup of steroids and play an important role in modulating growth hormones like androgens, estrogens, and glucocorticoids [7].

There are two main types of sterols: plant sterols (phytosterols) and those derived from animal tissues (cholesterol) [8]. They are often found as waxy solids at room temperature.

Phospholipids

Phospholipids are a type of lipid that are a major component of all cell membranes [9]. They are amphipathic molecules, meaning they have a hydrophilic (water-attracting) phosphate-containing head and two hydrophobic (water-repelling) fatty acid tails. Phospholipids are found in small amounts in various foods, such as egg yolks, fatty fish, spinach and some fruits.

Interestingly, all three of these lipids can also be found in skincare and lip balm products. Being rich and fatty, they tend to make an excellent skin barrier cream and a soothing salve for irritation!

The functions of lipids in the body

Lipids are essential for life. They play several key roles in the human body, including:

Energy storage and organ protection

You can think of lipids (specifically, triglycerides) like an energy reserve. They're stored in adipose tissue (otherwise known as body fat). When needed, they are broken down into fatty acids and glycerol so they can be used as an energy source. Through a process called beta-oxidation, lipids produce acetyl co-enzyme and generate ATP — the cell's energy currency [10].

Lipids — and, fat tissue more broadly — also play a crucial role in cushioning our organs. They help to keep our heart, kidneys, liver (and more) safe from body temperature changes and physical impact [11].

Cell health and production

Lipids support cell health by providing structural components for cell membranes. Phospholipids in particular create a protective barrier around the cell and its internal organs [12]. Lipids are also involved in cell signalling pathways, helping to transmit messages within and between cells [13].

Hormone production  

There's a reason that if women lose too much body fat, they risk losing their period (a process called amenorrhea). Lipid molecules help to regulate hormones, including the female sex hormones estrogen and progesterone [14].

Other fat-soluble hormones, like thyroid hormones, are also derived from lipids and are crucial for regulating metabolism, growth, and development [15].

Nutrient absorption and metabolism

Lipids also play an important role as chemical messengers for essential nutrients. Some vitamins (such as vitamin A, D, E and K) are fat-soluble, meaning they can only be absorbed in the presence of fat [16]. Dietary lipids bind to these vitamins and help them pass through the digestive system and into the bloodstream. Meaning, you get more of the good stuff in your body!

Here's where it gets really interesting. Lipids also regulate metabolism by providing energy through fat oxidation, acting as structural components of cell membranes, and serving as signalling molecules for cellular processes like hormone synthesis and gene expression [17]. So, in other words, dietary fat can prevent you from gaining body fat. Fancy that!

The role of lipids in foods

Lipids play an important role in our diets because they deliver a concentrated dose of energy. When you hear people talk about incorporating 'good fats' into your diet, they are likely referring to lipids.

Food sources to help maintain healthy lipid levels

Lipids can be found in both solid and oil form, and are derived from both animal-based and plant-based sources. Here are some of the heavy hitters:

Olive oil

You've likely heard olive oil being praised for its longevity benefits as part of the Mediterranean Diet — and lipids are a big reason why. Regardless of the type, it's high in monounsaturated fatty acids, containing about 75% in volume [18]. There's also research to show that swapping out oils high in saturated fat for olive oil can help lower LDL (bad) cholesterol [19].

Avocado

Not only is avocado one of the most versatile foods (you can enjoy it any time of day!), It's also a great source of lipids. Avocado lipids are primarily monounsaturated fats, with oleic acid being the most abundant fatty acid, making up over half of the total fat [20]. Other lipids in avocados include saturated fatty acids like palmitic acid, and smaller amounts of alpha linolenic acid.

Fatty fish

Fatty fish are a strong, reliable source of dietary lipids because they naturally contain high levels of Omega-3 fatty acids [21]. These are essential fatty acids, which means your body can’t produce them on its own and needs to get them from food. Including fish like salmon, mackerel, or sardines in your diet can, in turn, support brain function and heart health.

Managing your lipids

It's always possible to have too much of a good thing, and fats and oils are no exception. Having too many lipids in your blood is linked to a condition called hyperlipidemia.

This is when you have a buildup of fatty deposits in your arteries. Typically, hyperlipidemia occurs due to high levels of 'bad' LDL cholesterol [22]. However, it can also be the result of high triglycerides, without enough 'good' HDL cholesterol to level it out.

To ensure you're consuming lipids in a healthy, balanced way, it can be helpful to think of them in three categories. Polyunsaturated fatty acids are 'green' foods — meaning, you can consume them to your heart's content. They include fatty fish like salmon, oils such as sunflower, corn, and soybean, and nuts and seeds like walnuts, flaxseeds, and sunflower seeds.

Then, there are saturated fats like fatty meats, dairy products, processed meats and dairy products. These would be in the 'yellow' category, in that they're good to eat in moderation, but you wouldn't want to overdo it every day.

Finally, you have your trans fats. Think, deep-fried foods, cakes, cookies and some types of margarines. Firmly in the 'red' category, this is the worst type of fat to consume as it raises bad 'LDL' cholesterol.   These are best kept for special occasions.

Testing for lipids

The best way to check your lipid composition is to get a lipid panel, otherwise known as a cholesterol test. This is a blood test that measures the different types of fats (lipids) in your blood, including total cholesterol, triglycerides, HDL (good) cholesterol, and LDL (bad) cholesterol. It's recommended that healthy adults between 20 and 65 give a lipid blood sample every 5 years, but this should be more frequently if you have risk factors like diabetes or high blood pressure [23].

You can get a lipid test from your doctor, via home testing kits or through your NDIS Free Health Check, if you're between the ages of 40 and 75. Testing your lipids is important because it can be an indicator of your risk of developing cardiovascular disease, type 2 diabetes and even some neurological disorders [24].

The link between lipids and weight

If you're struggling to lose weight, getting your lipids tested can also help you get to the bottom of why. Research shows a link between excess lipids and insulin resistance [28]. This is a condition that prevents glucose from being used efficiently, which can lead to storing energy as visceral or subcutaneous fat.

The complex relationship between lipids and body fat is a testament to why weight loss can be so challenging. This is why Juniper's Weight Loss Programme takes a biological approach. By addressing the factors that impact body weight and metabolism — and pairing medical treatments with health coaching — we help you lose weight reliably and actually keep it off.

You can check your eligibility here.

Image credit: Pexels