Dietary fats

Fats play many roles in the body, particularly during metabolism. Your body can produce most of the required fats. Fats are also important in the enjoyment of food, improving its taste and feeling of satisfaction.

Fats and energy

All fats are high in energy, providing 37 kilojoules (kJ) per gram. In comparison, proteins and carbohydrates - the other two macronutrients that act as building blocks and sources of energy in the body - provide around 17 kJ.

It is difficult to maintain a healthy weight while eating high amounts of fats, particularly if you are not very physically active. Carrying extra weight (or being obese) is associated with an increased risk of a number of serious health conditions, including heart disease and type 2 diabetes.

Dietary fats shoul make up between 20-35% of all the energy you consume. It is also important to eat the right types of dietary fat.

Types of dietary fats

There are a number of different fats in food and it helps to know a little about their chemistry to understand why they can have such different effects on your health.

Triglycerides

Triglycerides are the most common type of fat found in foods. They get their name because they consist of one molecule of glycerol combined with three molecules of fatty acids (fats). It is the differences between the fatty acids in triglycerides that are important for your health.

Saturated fatty acids

In saturated fatty acids (SFAs) (or saturated fats), the carbon atoms of the fatty acid molecules attach to as many hydrogen atoms as possible - and so are 'saturated' with hydrogen. Therefore, due to their chemical structure, saturated fats tend to be solid at room temperature. They are found in:

• Red meats, particularly in the cuts with visible white fat;
• Chicken, particularly in the skin;
• Dairy products such as milk, cream, butter and cheese;
• Coconut products, and;
• Palm oil.

Saturated fats can be produced within the body, so there is no actual need to consume them. However, because they are present in meats and full-fat dairy foods and are also often used for baking or frying, they are found in a wide range of products, particularly biscuits, cakes, pastries and fast foods such as hot chips, pizzas and burgers.

Unfortunately, when you eat saturated fats, they can increase the amount of harmful low-density lipoproteins (LDLs), which contain more cholesterol and triglycerides than protein, in your bloodstream. This can lead to blockages in blood vessels and an increased risk of heart disease and conditions such as heart attack and stroke.

Adults should limit saturated fat to no more than 10% of their daily energy intake.

To do this you can:

• Choose lean meats and trim off the skin and white fat before cooking;
• Opt for lower-fat dairy options (except for children under two);
• Cook using the healthier mono-unsaturated and polyunsaturated fats;
• Read the packaging on processed foods for the saturated fat content and choose products with lower amounts of saturated fats, and;
• Limit fast foods (those with high amounts of saturated fats).

You do not have to cut out your favorite treats altogether, but it is important to remember they are treats. Only eat them occasionally and keep the serving size small.

Foods high in saturated fats can include foods such as chips, pizza and dairy products. 

Mono-unsaturated fatty acids

The mono-unsaturated fatty acids (MUFAs) contain one double carbon bond in the fatty acid molecules, so they have slightly fewer hydrogen atoms and are therefore called 'unsaturated'.

MUFAs tend to be liquid at room temperature and are found in:

• Avocados;
• A variety of nuts (including nut butters and nut oils) and seeds;
• Canola oil, and;
• Olives and olive oil.

MUFAs are produced within the body, but they may offer some health benefits, particularly when they are used instead of saturated fats.

Polyunsaturated fatty acids

Polyunsaturated fatty acids (PUFAs) contain two or more carbon bonds in the fatty acid molecules. This means they have fewer hydrogen atoms than MUFAs and so are called 'polyunsaturated'.

There are two main types of PUFAs: omega-6 and omega-3. The body cannot make these fats so they need to be consumed as part of your diet. PUFAs can help to reduce the levels of harmful low density lipoprotein (LDL) cholesterol in your bloodstream and therefore help to protect you from heart disease. Omega-3 PUFAs can also help to lower inflammation in the body.

There is ongoing research and debate about what is the healthiest balance of omega-6 and omega-3 PUFAs in the diet. In western diets, people tend to consume much more omega-6 than omega-3.

Omega-6 PUFAs can be found in:

• Vegetable oils such as sunflower, safflower and soybean, and;
• A variety of nuts and seeds.

Omega-3 PUFAs can be found in:

• Oily fish such as sardines, salmon, trout and tuna;
• Ground flaxseed and flaxseed oil;
• Canola and soybean oils, and;
• A range of nuts and seeds.

Compared to those obtained from fish sources, the body finds it more difficult to use omega-3 PUFAs from plant sources such as nuts, oils and seeds.

Foods high in unsaturated fats include nuts, avocado and fish. 

Trans fats

Trans fats are polyunsaturated fats that are chemically changed by a process called partial hydrogenation. This is sometimes done in the production of processed foods because it means that this type of fat is less prone to spoiling and easier to cook with.

Trans fats can be found in:

• Butter;
• Some margarines, and;
• Many processed foods.

Even more than the saturated fats, trans fats can increase the levels of unhealthy LDLs in your blood, leading to an increased risk of heart disease.

It is recommended that people minimize their consumption of trans fats. You can do this by checking the levels of trans fats on the packaging of processed foods that you buy and choosing options that are low in trans fats.

For a healthy option during cooking, use oils that are rich in unsaturated fats, such as sunflower and canola. 

Cholesterol

Cholesterol is a fat that is produced by animal cells and performs many important functions in the body, including:

• Helping to form cell membranes;
• Contributing to hormone production;
• Contributing to the production of bile, which aids digestion, and;
• Helping to produce vitamin D.

Cholesterol is also found in all foods made from animal products, particularly in eggs, seafood, fatty meats and full-fat dairy products.

The body can produce cholesterol, so it is not necessary to consume it as part of your diet. Consuming cholesterol can increase its levels in the blood, although not as much as consuming saturated or trans fats.

Cholesterol can pose a risk to health because of the way it is transported in the bloodstream.

Cholesterol containing LDLs are the main form of cholesterol in the blood. When levels are high, it can cause blockages in blood vessels that can block blood supply to vital organs.

However, not all cholesterol is harmful. In contrast with LDLs that have a higher composition of cholesterol than protein, high-density lipoproteins (HDL) contain 50% protein in addition to cholesterol and triglycerides. These proteins also circulate in the bloodstream. They help to move cholesterol and other fats to the liver for disposal, hence helping to reduce risk of artery blockages and development of heart diseases.

Most healthy people do not need to avoid cholesterol-rich foods such as eggs and seafood, which in moderate amounts are very nutritious and part of a healthy diet. It is more important to limit the amount of saturated fats and trans fats that you consume.

You can help to keep your blood cholesterol levels healthy by:

• Choosing low-fat dairy products and limiting higher-fat products such as cheese;
• Consuming leaner meat cuts with the fat trimmed off instead of fatty meats or processed meats such as salami;
• Use polyunsaturated margarine instead of butter;
• Eating plant-based foods that are high in fiber, which has been shown to help lower cholesterol levels;
• Being physically active, which can help to raise HDL levels while lowering levels of LDL in the bloodstream, and;
• Quitting smoking.

Phytosterols

Phytosterols (also known as plant sterols) are fats that are very similar to cholesterol, but are produced by plants. When phytosterols are consumed, they reduce the amount of cholesterol our bodies can absorb, but are not easily absorbed themselves.

They can be found in:

• Vegetable oils including sunflower and canola;
• Nuts;
• Legumes;
• Vegetables;
• Fruit, and;
• Wholegrain-based foods.

In an average diet, these sources only provide a small amount of phytosterols - not enough to significantly affect blood cholesterol levels. However, higher levels of phytosterols can be added to foods such as margarine that, when consumed in recommended amounts, can help to lower your blood cholesterol levels. Your doctor can discuss whether foods fortified with phytosterols are appropriate for you.

Maintaining a healthy diet

You can enjoy foods that contain fats as part of eating a healthy, balanced diet by:

• Eating plenty of fresh foods such as vegetables and fruits that are low in fats and energy and high in nutrients and fiber;
• Eating wholegrain foods;
• Consuming small amounts of foods rich in healthier unsaturated fats, such as nuts, seeds and some oils;
• Eating limited amounts of foods rich in cholesterol;
• Limiting saturated fats and avoiding trans fats, particularly in processed foods, which also tend to be high in sugar and low in nutrients, and;
• Making sure you balance your energy intake with your energy needs. Being physically active on most days can help with this.

Moderate amounts of different fats can be a part of healthy meals.