The ‘eat low fat’ mantra of the late 20th century has changed its tune in some surprising ways. So what sort of fat — and how much — should we eat? Healthy Food Guide nutritionist Rose Carr goes on a fat-finding mission.
In the 1970s and ’80s, we were told that we would all be healthier if we followed a low-fat diet. The thinking was that, by reducing our total consumption of fat, we would cut our saturated-fat intake. We also thought that to lose weight and keep it off, we needed to follow a low-fat diet. Sounds reasonable? Well, it caused some unpredicted changes to our eating habits.
On the back of this well-meaning advice, food manufacturers created a rush of low-fat packaged foods: yoghurt, mayonnaise, salad dressings and even chocolate biscuits. “Now we can eat all our favourite foods, without the fat!” we thought, as we tucked into a bowl of 99 per cent fat-free ice-cream. However, to help make these foods more palatable, manufacturers added more sugar. So while we thought they were a healthier and lighter alternative, the reality was that many low-fat products had the same, if not more, kilojoules as the original.
In taking out the fat, they also removed a key trigger that causes us to feel satisfied after eating. Fat creates a luxurious, rich mouthfeel, whereas it’s easy to overeat fat-free products, especially if you think they’re doing you good. So we kept eating our low-fat foods, and, much to our surprise, we kept gaining weight.
Full-fat, low-fat, good fat, bad fat… there is a lot of confusion about what’s really healthy. As nutritional science evolves, fats are enjoying something of a comeback.
Why we love fat
Per gram, fat has twice the kilojoules of protein or carbs. But there’s more to fat than just kilojoules. It is filling – compare creamy, full-fat yoghurt to the watery, skim variety – and it adds texture and flavour; that’s why high-fat foods taste good. Fat also slows digestion, which helps to keep blood-sugar levels steady and to control appetite. On a low-fat diet, you may not feel as satisfied, especially if you eat high-GI, processed carbs instead.
Types of dietary fat
While a lower-fat diet might suit some people for weight loss, for others it’s not helpful. It’s important to think about the types of fats you’re eating, as well as the amounts.
Saturated vs unsaturated
Fats are either saturated or unsaturated. Because of their structure, saturated fats can pack together tightly, and at room temperature they form a solid fat. Think coconut oil, palm oil and butter. Unsaturated fats are liquid at room temperature — for example, olive, canola, sesame and rice bran oils.
Unsaturated fats can be polyunsaturated or monounsaturated. Avocados, some nuts, and cooking oils made from plants or seeds are good sources of monounsaturated fats. Polyunsaturated fats are either omega-3 or omega-6, which are essential for the human body. While our bodies can make some fats, they can’t produce these, so we must get them from our diet. Good sources include oily fish, tahini, linseed (flaxseed) and chia seeds, oils made from seeds, and certain nuts.
Why we need fat
We need a certain amount of fat in our diet to stay healthy.
Vitamins A, D, E and K are fat-soluble — meaning, they transport themselves around our body via fats. Therefore, if we don’t eat fats, our bodies can’t absorb these vitamins.
Fats are also much more energy-dense than protein or carbs. If we need to put on weight, or we’re using more energy for extra activity, by upping our fat intake, we won’t need to increase the amount of food as much.
Finally, fat acts as insulation, which keeps us warm and helps protect our organs. However, too much abdominal fat around our organs is unhealthy.
Fats that love us
Plant foods, such as olives, avocados, nuts and seeds, and their oils, are all high in healthy unsaturated fats. The exceptions to the ‘plant food’ rule are coconut, palm kernel and palm oil, which are all high in saturated fats.
How to get more
Splash extra virgin olive oil over vegetables and salad leaves before serving — it helps your body absorb the antioxidants in the vegies.
Swap butter for avocado on sandwiches, toast and wraps, and make it into guacamole.
Experiment with nut and seed butters, such as tahini in salad dressings and natural peanut or almond butter in smoothies or on porridge.
‘Long-chain’ omega-3 fats are mainly found in oily fish. Higher intakes of long-chain omega-3s are beneficial to heart health, and potentially reduce your risk for dementia, diabetes and asthma. The dietary guidelines recommend eating oily fish, such as salmon or tuna, two or three times a week.
How to get more
Stash canned tuna in the pantry to quickly fold through pasta and vegies for a fuss-free dinner.
Enjoy sardines on toast for breakfast.
Order grilled salmon instead of battered fish when eating out.
Nuts ‘n stuff
‘Short-chain’ omega-3 fats are found in such plant foods as walnuts, flaxseeds and oil, pumpkin seeds, legumes and canola oil. Your body’s ability to convert short-chain omega-3 fat to long-chain omega-3 is limited. Although the message about the good fats in nuts has been around for several years, some people are still concerned that eating nuts will lead to weight gain. Research shows that the opposite is true: nut-eaters tend to weigh less than those who avoid them.
How to get more
Nibble on a small handful (30g) of unsalted nuts for a satisfying snack.
Top your morning cereal, muesli or yoghurt with chopped nuts and fresh or frozen fruit.
Toss toasted nuts through a salad or over steamed vegies for extra crunch and flavour.
Fats that don’t love us
Saturated fats mainly come from the visible fat on meat, as well as dairy products and processed foods like biscuits and takeaways. They are associated with atherosclerosis — the early stages of heart disease.
Last year, the World Health Organization published a review which found the best effects for total and lower LDL (‘bad’) cholesterol occurred when consumption of polyunsaturated fat (either omega-6 or omega-3 fats) increased, while saturated-fat intake decreased.
You should limit foods that are rich in saturated fats, such as fried foods, pastries and bacon.
Is the link between saturated fat and heart disease still valid?
Rates of death from heart disease have dropped dramatically since their peak in the 1960s, and reduced intake of saturated fats has been an important part of that.
A study published in 2016 takes it even further, linking increased saturated-fat intake with higher death rates from specific causes. The study followed about 125,000 people for more than 30 years, finding all-cause mortality increased with a higher saturated-fat intake, and decreased with higher intakes of both polyunsaturated and monounsaturated fats.
So the overall advice remains: we should reduce our intake of saturated fats and replace them with healthier unsaturated fats from foods like fish, nuts, avocado, olive oil and seeds.
Where do dairy foods sit?
It’s important to acknowledge that not all fats are equal — and this is true for saturated fats. More and more research shows that some foods are less-harmful sources of saturated fats than others. An analysis of 76 studies found cheese and whole-milk dairy products were associated with a reduced risk for heart disease, whereas saturated fat from meat increased this risk, as expected. One explanation is that the package of nutrients in dairy foods as a whole is protective.
A clinical trial also found that cheese did not raise LDL cholesterol, based on its saturated-fat content. But we still need to take care with portions: in this study, the intakes for saturated fat were considerably lower than our average servings, which may be an important factor.
Is butter better?
Despite how natural it is, butter has not changed from being a concentrated source of saturated fat that we should try to limit. Olive, canola, sunflower, rice bran and other unsaturated oils have been shown to be better for us. This doesn’t mean we need to banish butter — just use it in small amounts.
Is full-fat the way to go?
Whether you need to eat more or less fat really depends on your starting point and what suits you. Generally, low-fat diets are no longer recommended as the best way to shed kilos and maintain weight loss. However, it’s important to remember that everyone is different and a low-fat diet may suit some people more than others.
Take a look at healthy-eating patterns around the world. They can be low in fat, as in the traditional diet of Okinawans in Japan, or quite high, such as in a traditional Mediterranean way of eating that includes plenty of olive oil, nuts, fish and dairy foods, such as yoghurt.
Fat is kilojoule-dense, but it also fills you up and enhances texture, mouthfeel and taste — and enjoyment of food is part of a happy, healthy life. For weight loss, reduce overall kilojoule intake by watching portion sizes, and for a healthier diet, replace saturated fats with unsaturated fats. The best diet has lots of variety and is one you can stick to forever.
Getting the balance right
You don’t have to eliminate saturated fat completely — everything in moderation!
Choose these healthy fats
Oily fish: choose mackerel, herring, sardines, salmon and tuna for their healthy long-chain omega-3 fats
Nuts and seeds: aim to eat 30g (a small handful) a day
Avocado: a heart-healthy butter alternative when in season
Extra virgin olive oil: this versatile oil is high in monounsaturated fats
Nut and seed oils: canola, rice bran, sesame, and other nut and seed oils
Limit these unhealthy fats
Fried foods, pies, hot chips, pastries, biscuits, doughnuts and cakes
Fatty meats: look for lean cuts of red meat and remove skin from chicken
Processed deli meats (such as ham, bacon, salami):
Butter: seek out healthier alternatives, such as avocado, tahini or hoummos
High-fat cheeses: harder cheeses can be especially high in sat fat, so stick to small 40g portions (about two slices).
Full-fat milk and yoghurt: if you are watching your weight, reduce overall kilojoule intake by choosing reduced-fat, unsweetened alternatives.
Cream: use only when nothing else will do, and preferably a reduced-fat version; otherwise, choose alternatives, such as Greek-style yoghurt.
Coconut and coconut fat: a 2014 review of the evidence found it is not as good for us as unsaturated plant oils.