Fat is one of the most talked-about nutrients and one of the most misunderstood. Dietitian Nicole Senior answers the 21 most frequently asked questions about fat to help you make healthier choices.
1. What are fats?
Fat is one of the four macronutrients found in food, along with water, protein and carbohydrate (alcohol is also a nutrient but not essential). Fats are a group of chemically similar substances composed of fatty acids. They include liquid oils such as olive oil, as well as solid fats such as butter, ghee, lard and copha.
2. Is a fat-free diet healthy?
No! It's necessary to include some fat in our diet because fats provide essential fatty acids, fat-soluble vitamins and a concentrated form of energy. Fatty acids are needed to build and maintain cell membranes, and to make certain hormones. So we need to eat fat but it's important to choose the right type of fat.
3. How did fat develop such a bad reputation?
Saturated fat is the main culprit in raising cholesterol levels and heart disease rates. However, there are other types of fats that are essential for good health.
4. Which fats are the good ones?
Fats are classified as saturated or unsaturated, depending on their chemical structure. Unsaturated (good) fats include polyunsaturated and monounsaturated types and are better for you because they help maintain healthy cholesterol levels. Polyunsaturated 'good' oils include sunflower, safflower, soy bean, corn, walnut and sesame oils. Monounsaturated 'good' oils include olive, canola, avocado, macadamia and peanut oils.
5. Why do I love fatty foods so much?
Humans are driven by a powerful survival instinct based on a 'feast or famine' environment. Although times have changed and now food is plentiful, we are still pre-programmed to eat high-energy foods so that, should food become scarce, we will have a better chance of surviving. We also tend to eat more fat than is good for us because fat is full of flavour and gives foods such as pastry, biscuits and deep-fried fish and chips a pleasant crunchy texture. Food manufacturers also often add fats to many foods to improve flavour and texture, so you may be eating more fat than you realise.
6. Is fat really fattening?
Although fat is the most energy-dense nutrient (containing 37 kilojoules per gram), any food can cause weight gain if the total amount of kilojoules you eat is more than you need. Obesity rates have increased without any apparent increase in the amount of fat we eat.
7. Which fats should I be eating less?
Eat minimal amounts of saturated fats found in fatty meat, butter, cream, whole milk and dairy foods, processed foods containing palm oil, and many deep-fried takeaway foods. Chocolate and coconut products such as copha and coconut cream are also rich in saturated fat.
8. Which is healthier: butter or margarine?
Table margarine is more accurately termed 'oil-spread' in Australia and New Zealand, and is recommended as a healthier choice than butter by the Dietary Guidelines for Australians and the Heart Foundation. Oil-spread is better because it is made with healthy oils and therefore contains much less saturated fat than butter. Contrary to popular belief, oil-spreads are not a major source of trans fats. Check the nutrition information panel, or look for an oil-spread with the Heart Foundation Tick.
9. How much fat should we eat?
Between 20-35% of our daily kilojoule intake should be fat. In a typical diet of 8700kJ, this is between 50-80g of fat each day. Fat is already present in some foods, so a healthy amount to use is between 1 1/2 and 2 1/2 tablespoons of healthy oils and oil-spreads a day. You may need a little less or a little more, depending on your energy needs. Saturated fat should make up no more than 10% of daily kilojoules, or no more than 20g in a typical diet.
10. I'm trying to lose weight. How much fat can I eat?
To lose weight, you need to eat fewer kilojoules. In order to stay healthy, your diet must still be balanced, so the proportion of fat in your diet should not fall too low or you may not eat enough essential fats – 30% of your daily kilojoules is about right. In a typical weight-loss diet of 6000kJ, this is 50g of fat daily. Most of this should come from healthy, added 'good' fats (oils and oil-spreads).
11. Which is the best oil to use?
Any oil made from vegetables, seeds or fruits is good (see question 4 above). Coconut and palm oils are the exceptions to this rule: avoid them as they are both high in saturated fat.
12. How should oils be stored?
Store in a cool dark place (not next to the stove). Buying oil in tins will help protect it from light; if you buy olive oil in a bottle, keep it in a cupboard away from light. Use oil quickly rather than storing it for long periods – try buying it in smaller quantities to keep it fresh.
13. How will I know if the oil has gone off?
Oil that has oxidised, or gone rancid, has a characteristic stale, musty smell. Don't use rancid oil. Healthier oils go rancid more easily than unhealthy ones, so eat them quickly and store them correctly.
14. What is 'extra-virgin' olive oil?
Extra-virgin oil is from the first mechanical pressing of the olives and is rich in antioxidants. The alternative, refined oil, is produced when the pulp is further processed to extract every last drop of oil.
15. Can I cook with extra-virgin olive oil?
Regular olive oil has a higher smoke point and is better to use in cooking than extra-virgin. Extra-virgin olive oil is also pricier.
16. Is it safe to re-use oil?
Reheating will cause oils to oxidise and degrade, but some do this more slowly. Polyunsaturated oils are the most readily oxidised, but monounsaturated oils such as olive oil are more stable and can be re-used. Be sure to strain out any bits of food left in the oil, store in a sealed jar after cooling, and only re-use it a few times.
17. How much salad dressing and mayonnaise can I use?
Mayonnaise and salad dressings are usually made with healthy oils but commercial ones can be quite salty. It's best to make your own and use in moderation.
18. What's the latest on canola oil?
Canola oil is predominantly monounsaturated and it also has some short-chain omega-3 fatty acids (see box below). It's recommended as a healthy choice by the Heart Foundation.
19. What are trans fats?
Trans fats are a particular type of bad fat that should be limited because they adversely affect cholesterol levels. They are naturally present in low levels in butter and meat fat, but are produced in higher amounts when liquid oils are partially hydrogenated to make them solid. They are often used commercially to make pastry, biscuits and cakes. Commercial deep-frying oils also tend to contain trans fats, although one prominent fast-food chain has already switched to a low-trans frying oil. Eating a diet low in saturated fats will help you eat less trans fats as well.
20. What's so good about rice bran oil?
Rice bran oil is a mostly monounsaturated oil that contains small amounts (around 1%) of a naturally occurring plant sterol called oryzanol that can help lower cholesterol absorption. It has a high smoke point so it's good for frying.
21. What are omega-3 fatty acids?
Why we need them
Omega-3 fatty acids are essential polyunsaturated fatty acids. Our bodies can't make them so we need to obtain them from our diet. Omega-3 refers to both short-chain fatty acids (plant foods) and long-chain fatty acids (animal foods). It's best to eat a mix of both.
Where to find them
Plant foods such as canola and soy bean oils, linseeds and walnuts are the best sources of omega-3 short-chain fatty acids. The richest source of long-chain fatty acids is oily seafood (especially salmon, sardines and mackerel), and also brains, liver, kidneys, eggs and lean red meat - especially pasture-fed beef, lamb and kangaroo. Fish-oil capsules can help boost your omega-3 intake.
What they do
Omega-3 fats are linked to better heart and mental health, a reduced risk of inflammatory diseases, and improved brain development in kids.
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