What do fats and oils do in the body, how do saturated and unsaturated fats differ, and why does the type of fat matter for health?
Explain the functions of fats and oils, distinguish saturated from unsaturated fats, and relate fat type to health
A focused answer on fats and oils - their functions as concentrated energy, insulation and vitamin carriers, the difference between saturated and unsaturated fats, and how fat type affects heart-disease risk.
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What this dot point is asking
The syllabus wants you to explain why the body needs fat, to tell saturated and unsaturated fats apart, and to connect the type of fat to health, especially heart disease. The big idea is that fat is essential and useful, but the amount and the type matter: too much fat is fattening, and too much of the wrong (saturated) type harms the heart.
The answer
Fats and oils are the same nutrient
Fats and oils are chemically the same kind of nutrient. The difference is simply state at room temperature: fats are solid (butter, lard) and oils are liquid (sunflower oil, olive oil). Both are made of fatty acids and glycerol.
Functions of fat
- A concentrated source and store of energy. Fat gives , more than double protein or carbohydrate, and the body stores spare energy as body fat.
- Insulation and protection. A layer of fat under the skin keeps the body warm, and fat around organs such as the kidneys protects them from injury.
- Carrying fat-soluble vitamins. Vitamins A, D, E and K dissolve in fat, so some fat in the diet is needed to absorb them.
- Making food palatable. Fat adds flavour, a smooth texture and a feeling of fullness.
Saturated versus unsaturated fat
Saturated fats are usually solid at room temperature. They come mainly from animal foods (butter, cheese, fatty meat, lard) and from a few plant oils such as coconut and palm oil. A high intake raises the level of cholesterol in the blood.
Unsaturated fats are usually liquid (oils) at room temperature. They come mainly from plants and oily fish (olive oil, sunflower oil, nuts, salmon, mackerel). They are the healthier choice and can help keep blood cholesterol lower.
Fat type and health
Eating too much saturated fat raises blood cholesterol. Excess cholesterol can be deposited in the walls of arteries, narrowing them. This restricts blood flow and increases the risk of coronary heart disease and stroke. Replacing some saturated fat with unsaturated fat, and cutting the total amount of fat, lowers this risk. Because fat is so energy-dense, a high-fat diet also makes weight gain and obesity more likely.
Examples in context
Example 1. Deep-fried versus steamed. A piece of fish that is deep-fried soaks up oil and gains a lot of fat and energy, while the same fish steamed keeps its naturally healthy unsaturated fats with little added. The cooking method, not just the food, decides the fat content of the meal.
Example 2. Coconut milk in local cooking. Dishes such as laksa and rendang rely on coconut milk, which is a plant product but high in saturated fat. Using light coconut milk or thinning it with stock keeps the flavour while reducing the saturated fat, a practical adaptation for a heart-healthy version of a familiar dish.
Try this
- Cue. State three functions of fat in the body. Recall concentrated energy, insulation and organ protection, and carrying fat-soluble vitamins.
- Cue. Explain how a diet high in saturated fat can lead to heart disease. Link saturated fat to raised blood cholesterol, to fatty deposits narrowing the arteries, to reduced blood flow and heart disease.
- Cue. Give two examples of foods high in unsaturated fat and one plant oil that is high in saturated fat. Name olive oil, sunflower oil or oily fish for unsaturated, and coconut or palm oil for the saturated plant oil.
Exam-style practice questions
Practice questions written in the style of SEAB exam questions on this dot point, with worked answer explainers. The year tag is the paper they imitate, not the source.
Original6 marksState three functions of fat in the body. Explain the difference between saturated and unsaturated fats, giving one food source of each.Show worked answer →
Three functions: fat provides a concentrated source and store of energy; it insulates the body to keep it warm and protects organs; and it carries the fat-soluble vitamins A, D, E and K.
Saturated fats are usually solid at room temperature and come mainly from animal foods such as butter, fatty meat and coconut oil; a high intake raises blood cholesterol. Unsaturated fats are usually liquid (oils) at room temperature and come mainly from plants and oily fish, such as olive oil or salmon; they are the healthier choice.
What markers reward: three distinct functions, a correct saturated-versus-unsaturated distinction (solid/animal versus liquid/plant), a source for each, and the link from saturated fat to raised cholesterol.
Original4 marksA hawker dish is deep-fried in palm oil and served with fatty pork. Explain why eating it often could harm health, and suggest two ways to make a similar meal lower in saturated fat.Show worked answer →
The dish is high in saturated fat from the fatty pork and the deep-frying. Eating it often raises blood cholesterol, which can lead to fatty deposits in the arteries, narrowing them and increasing the risk of coronary heart disease, as well as adding a lot of energy that can cause weight gain.
Two improvements: choose a leaner cut of meat or trim the fat, and cook by steaming, grilling or stir-frying in a small amount of unsaturated oil instead of deep-frying.
What markers reward: the saturated-fat to cholesterol to heart-disease chain, the energy-and-weight point, and two realistic changes that cut saturated fat (leaner meat, healthier cooking method).
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