Too much fat in your diet, especially saturated fats, can raise your cholesterol, which increases the risk of heart disease.
Current UK government guidelines advise cutting down on all fats and replacing saturated fat with some unsaturated fat.
But the question should not be about choosing between fat or sugar: there are good reasons for cutting down on both.
Cutting down on saturated fats is only one aspect of reducing your risk of heart disease, stroke and other cardiovascular diseases. Other risk factors include eating too much salt and sugar, being overweight, smoking and a lack of physical activity.
When it comes to heart health, you are better off focusing on your overall diet than on individual nutrients such as fat or sugar. A balanced and nutritious diet is considered one of the best ways to reduce your risk of developing cardiovascular diseases.
A small amount of fat is an essential part of a healthy, balanced diet. Fat is a source of essential fatty acids such as omega-3 – "essential" because the body can't make them itself.
The fat you eat is broken down during digestion into smaller units of fat called fatty acids. Any fat not used by your body’s cells or to create energy is converted into body fat. Likewise, unused carbohydrate and protein are also converted into body fat.
All types of fat are high in energy. A gram of fat, whether saturated or unsaturated, provides 9kcal (37kJ) of energy compared with 4kcal (17kJ) for carbohydrate and protein.
The main types of fat found in food are saturated fats and unsaturated fats. Most fats and oils contain both saturated and unsaturated fats in different proportions.
As part of a healthy diet, we should try to cut down on foods and drinks high in saturated fats and trans fats and replace some of them with unsaturated fats.
Frequently eating more energy than you need, whether it’s from fat, carbohydrate or protein, increases your risk of becoming overweight or obese, which can increase your cholesterol.
Saturated fats are found in many foods, both sweet and savoury. Most of them come from animal sources, including meat and dairy products, as well as some plant foods such as palm oil.
Foods high in saturated fats include:
While any type of fat in our food can be turned into cholesterol by the body, it's the "sat fat" we need to cut down on because we're eating too much of it.
Cholesterol is mostly made in the liver from any type of fat you eat. It's carried in the blood in two ways: as low density lipoprotein (LDL) and high density lipoprotein (HDL).
Too much LDL cholesterol can lead to fatty deposits developing in the arteries, which can restrict the flow of blood to the heart and brain, increasing the risk of heart disease and stroke.
On the other hand, HDL cholesterol has a positive effect by taking cholesterol from parts of the body where there is too much of it, to the liver, where it is disposed of.
Eating too much fat and sugar can also increase the level of triglycerides, a fatty substance mostly made by the liver. High levels of triglycerides in the blood have also been linked with narrowing of the arteries.
Most people in the UK eat too much saturated fats. The population on average gets 12.6% of their energy (kJ/kcal) from saturated fats, which is slightly above the 11% maximum recommended by the government.
Trans fats are found naturally at low levels in some foods, such as those from animals, including meat and dairy products.
Trans fats can also be found in hydrogenated vegetable oil. Hydrogenated vegetable oil must be declared on a food's ingredients list if present.
Like saturated fats, trans fats can raise cholesterol levels in the blood. This is why it's recommended that trans fats should make up no more than 2% of the energy (kJ/kcal) we get from our diet. For adults, this is no more than about 5g a day.
However, most people in the UK don't eat a lot of trans fats. On average, we eat about half the recommended maximum. Most of the supermarkets in the UK have removed hydrogenated vegetable oil from all their own-brand products.
We eat a lot more saturated fats than trans fats. This means that when looking at the amount of fat in your diet, it's more important to focus on reducing the amount of saturated fats.
If you want to cut your risk of heart disease, it's best to reduce your overall fat intake and swap saturated fats for unsaturated fats. There is good evidence that replacing saturated fats with unsaturated fats can help lower cholesterol.
Found primarily in oils from plants, unsaturated fats can be either polyunsaturated or monounsaturated. Monounsaturated fats help protect our hearts by maintaining levels of HDL cholesterol while reducing levels of LDL cholesterol.
Monounsaturated fats are found in:
Polyunsaturated fats can help lower the level of LDL cholesterol. Replacing saturated fats with polyunsaturated fats may also help reduce triglyceride levels.
There are two types of polyunsaturated fats: omega-3 and omega-6. Some types of omega-3 and omega-6 fats cannot be made by the body and are therefore essential in small amounts in the diet.
Omega-6 fats are found in vegetable oils such as rapeseed, corn, sunflower and some nuts. Omega-3 fats are found in oily fish such as mackerel, kippers, herring, trout, sardines, salmon and fresh tuna.
While most of us get sufficient omega-6 in our diet, mostly from cooking oil, we're advised to eat more omega-3 by eating at least two portions of fish a week, including one of oily fish.
Vegetable sources of omega-3 fats are not thought to have the same benefits on heart health as those found in fish.
There are labelling guidelines set by the European Union to help you work out whether or not a food is high in fat and saturated fat.
The nutrition labels on food packaging can help you cut down on total fat and saturated fat (also listed as saturates, or sat fat).
For a product to be labelled lower fat, reduced fat, lite or light, it has to contain at least 30% less fat than a similar product.
But if the type of food in question is high in fat in the first place, the lower-fat version may also still be high in fat (17.5g or more of fat per 100g). For example, a lower-fat mayonnaise is 30% lower in fat than the standard version, but is still high in fat.
These foods also aren't necessarily low in calories. Sometimes the fat is replaced with sugar and may end up with a similar energy content. To be sure of the fat content and the energy content, remember to check the nutrition label on the packet.
Cutting down on fat is only one aspect of achieving a healthy diet. Find out more about how to get a balanced nutritious diet in the eatwell plate.
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