Dietary fats have gone through a lot over the years. After being shunned as the culprit for rising obesity and type 2 diabetes rates for decades (turns out, sugar is likely to blame for that), fat's image is now one of health and wellness. Nuts and seeds have replaced low-fat yoghurt as snacks, and more and more people are turning to high-fat, low-carb diets to try to manage obesity and related diseases.
Putting aside fat's back story, the truth is fat is a macronutrient essential to our health. Without enough fats in our diet, our skin, hair, hormones, energy levels and metabolic functions can suffer.
To understand more about fat, why we need it and what happens when we don't eat enough fat, HuffPost Australia spoke to Rebecca Gawthorne, accredited practising dietitian and nutritionist.
Why do we need to eat fats?
"Fat is an essential part of our diet and necessary for good health. Fats have many vital roles, including helping to absorb and transport fat-soluble vitamins (that is, vitamins A, D, E and K) around our body, protecting our organs and insulating us to keep us warm," Gawthorne told HuffPost Australia.
"Fats also provide our bodies with essential fatty acids which are required to build and maintain our cell membranes, which is important for our skin, hair, eyes, heart, brain and more. Fats also help make certain hormones and help you feel satiated -- to help you feel full."
What are the healthy and unhealthy types of fats?
When we're talking about dietary fat, it's important to note that not all fats are created equal. We need to focus on the 'healthy' fats and minimise our intake of the rest.
"There are different types of fats which are determined by their chemical structure, and some are healthier than others," Gawthorne said.
Unsaturated fats (monounsaturated and polyunsaturated fats)
"Unsaturated fats are 'healthy' fats and are an important part of a healthy diet," Gawthorne said.
There are two main types of unsaturated fats: polyunsaturated fats (PUFA) and monounsaturated fats (MUFA). Polyunsaturated fats include:
- Omega-3 fatty acids which are found in oily fish such as salmon, tuna, sardines and anchovies, walnuts, canola oil, soy products, flaxseeds and omega-3 enriched eggs.
- Omega-6 fatty acids which are found in some oils like safflower and soybean oil, along with some nuts and seeds such as sesame seeds, flax seeds, hemp seeds and pine nuts.
"Monounsaturated fats are also 'healthy' fats that are found in plant foods like avocados, olive oil and nuts like cashews and almonds."
Both monounsaturated and polyunsaturated fats tend to lower LDL blood cholesterol when they replace saturated fats in the diet. Studies have also shown the consumption of healthy fats is linked to lower risk of heart disease and better gut health.
"Saturated fats are aren't classified as 'healthy' fats because eating greater amounts of saturated fat has been found to be linked with high blood cholesterol, which a risk factor for heart disease," Gawthorne said.
While the evidence around saturated fats and heart disease is murky, at the moment most health experts agree that replacing saturated fat with polyunsaturated fat is a healthier option.
Saturated fats are solid at room temperature and are found in:
- Dairy foods -- butter, cream, ice cream, milk and cheese
- Meat -- red meat, processed meats and chicken
- Some plant-derived products -- coconut oil and cream, palm oil and cooking margarine
- Processed foods -- deep fried foods (e.g. chips, pies, battered foods), fatty snack foods, packaged cakes and biscuits, pastries and pies.
Of all the types of dietary fats, trans fats is the one to steer clear of most.
"Trans fats are classified as 'unhealthy fats' because they increase your level of bad (LDL) cholesterol and decreases the level of good (HDL) cholesterol in the body, which increases your risk of heart disease," Gawthorne said.
"Trans fats are actually unsaturated fats that have been processed and behave like saturated fats inside the body. Trans fats are found in processed foods like deep fried foods, commercial baked pies, pastries, cakes and biscuits. Spreads and margarines can also contain trans fats."
How much fat should we eat per day?
"Fats are essential in our diet and it's recommended that our total fat intake should be around 25-30 percent of our total energy intake," Gawthorne said.
"Saturated fat should be no more than 10 percent of our total energy intake, which leaves the remainder as unsaturated fats. It's recommended that we as much replace saturated and trans fats with unsaturated fats in the diet as we can."
To meet our daily recommended fat requirements, we should focus on eating nuts, seeds, avocado, olive oil and fatty fish.
"It's recommended that Australian adults have 250-500mg of marine omega-3s each day to reduce their risk of heart disease which can be achieved by having 2-3 serves (150g each) of oily fish per week, as well as having one gram of omega-3 from plant sources."
Tasty ways to enjoy healthy fats
- Add seeds (sesame seeds, pumpkin seeds, pine nuts) and nuts (almonds, cashews, walnuts) to salads and stir fry
- Use avocado as a spread and in salads
- Use natural nut and seed butters (peanut butter, tahini, almond butter) on whole grain toast or crackers
- Use extra virgin olive oil for salad dressings
- Stir fry and bake your veggies with olive oil
- Enjoy salmon, tuna and other fatty fish with your meals
- Snack on nuts and seeds
- Buy breads and crackers with seeds
- Add chia seeds, LSA and nuts into your smoothies and homemade snacks like muffins
- Add nuts and seeds to muesli, porridge and yoghurt
Does fat make you fat?
Many people still avoid nuts, seeds and avocado for fear these foods 'make you fat'. But is this true?
"When eaten in large amounts, all fats (including healthy fats) can contribute to weight gain," Gawthorne said.
In other words, it's all about the quantity of dietary fat you eat.
"Fat is higher in energy (kilojoules) than the other macronutrients (carbs and protein), so eating less fat overall is likely to help with weight loss. However, including unsaturated fats in moderate amounts in our diets is essential to health and healthy weigh loss or maintaining a healthy weight.
"If you are trying to lose weight, you should not follow a no-fat or low-fat diet, but instead aim to reduce your intake of saturated and trans fats, and replace them with moderate amounts of unsaturated fats."
9 signs you're not eating enough fat
As healthy fats help our bodies build and maintain cell membranes and absorb and transport vitamins, inadequate intake results in functions of these processes being impaired, Gawthorne explained.
Signs of inadequate fat intake include:
- Dry and scaly skin
- Dry eyes
- Feeling constantly cold
- Dry hair and/or hair loss
- Hormonal problems, including loss of menstrual cycle
- Inability to feel full/always feeling hungry
- Issues concentrating and/or mental fatigue
- Deficiencies in fat-soluble vitamins
- Constant fatigue