How much fat should we eat?

Urging people to follow low fat diets and lower their cholesterol is having "disastrous health consequences", according to a health charity.

The National Obesity Forum and the Public Health Collaboration are calling for a "major overhaul" of current dietary guidelines, claiming that the focus on low fat diets is failing to address Britain's obesity crisis.

The report cites snacking as a major cause of weight gain, and is calling for a return to "whole foods" such as meat, fish and dairy, as well as high fat foods including avocados, arguing that "eating fat does not make you fat".

However, Public Health England has labelled the report's advice to eat more fat as "irresponsible".

But what is the official advice on fats? Are they friend or foe? How much is too much, and should they be avoided altogether?

We take a look at NHS advice and answer your questions:

Is fat bad for you?

Yes and no, so long as it is eaten in moderation.

Eating too much fat, especially saturated fat, can raise cholesterol levels, which can increase your risk of heart disease, stroke, and cardiovascular diseases.

However, your body needs fats.

Fat is an essential source of essential fatty acids, such as omega-3. They are "essential" as our bodies cannot make them.

Fat is needed for the body to absorb vitamins A, D, and E. It's also required for the nerves and brain to function properly, maintaining healthy cells and skin, and it also provides a source of energy.

Is there just one type of fat?

No. There are different types of fat: saturated fat, unsaturated fat, and trans fats.

Saturated fat

Saturated fat is found in meat and dairy products, as well as some plant foods such as palm oil.

Too much saturated fat in our diets raises cholesterol levels.

There are two types of cholesterol. Low density lipoprotein (LDL), too much of which can lead to fatty deposits in the arteries, which restrict the flow of blood to the heart and brain, leading to an increased risk of strokes and heart disease. However, the other type of cholesterol, high density lipoprotein (HDL), takes cholesterol from parts of the body where there is too much of it, to the liver where it is disposed of.

Saturated fat increases LDL cholesterol levels, which is why too much of it is bad for you.

How much is too much?

Current Government recommendations on saturated fat consumption are that:

• The average man should not eat more than 30g saturated fat a day.

• The average woman should not eat more than 20g saturated fat a day.

• Children should eat less.

Unsaturated fat

Evidence suggests that replacing saturated fat with unsaturated fat can help to lower cholesterol levels.

Unsaturated fats tend to come from plant oils, and here's where it gets a little more complicated. Unsaturated fats are either polyunsaturated or monounsaturated.

What is monounsaturated fat?

Monounsaturated fats help to protect the heart by maintaining HDL cholesterol levels, and reducing LDL cholesterol.

Monounsaturated fats are found in:

• Olive oil and rapeseed oil

• Avocados

• Some nuts, such as almonds, Brazils, and peanuts

What is polyunsaturated fat?

Polyunsaturated fats also help to lower LDL cholesterol levels.They also help to lower triglyceride levels. Triglycerides are fatty substances made by the liver, and high levels of them in the blood can lead to the narrowing of arteries.

Polyunsaturated fats can be found in two types: omega-3 and omega-6. Neither of these can be made by the body, and so they must be eaten. However, only small amounts are needed.

• Omega-6 is found in vegetable oils such as rapeseed, corn, and sunflower oils, and some nuts.

• Omega-3 is found in oily fish such as fresh tuna, trout, mackerel, kippers, herring, salmon, and sardines.

Trans fats

Trans fats are found in naturally low levels in foods, such as meat and dairy products.

Artificial trans fats can be formed when oil goes through a process called hydrogenation, which makes the oil more solid (known as hardening). This type of fat, known as hydrogenated fat, can be used for frying or as an ingredient in processed foods.

However, foods must declare if they contain trans fats.

Like saturated fat, trans fats raise cholesterol levels.

Luckily, most supermarkets in the UK have removed hydrogenated fats from their foods, and as a result most people eat no more than 2.5g of trans fats per day. For adults the recommended maximum is 5g.

So, are foods lower in fat good for you?

For a food to be labelled as "lower fat", it must contain 30 per cent less fat than normal products.

While these foods may be lower in fat, they may still have a similar calorie content, as fat may have been replaced by sugar.

How do I know if food is high in fat or not?

Foods must display their nutritional content per 100g, and a traffic-light system is often used to show if foods are high or low in something.

EU guidelines provide the following advice:

• A food is high in fat if it has more than 17.5g of fat per 100g.

• A food is low in fat if it contains less than 3g of fat per 100g, or 1.5g of fat per 100ml of liquid.

• A food is described as fat-free if it has less than 0.5g of fat per 100g or 100ml.

There are also separate guidelines for saturated fats:

• A food is high in saturated fat if it has more than 5g of saturates per 100g.

• A food is low in saturated fat if it contains less than 1.5g of fat per 100g, or 0.75g of saturates per 100ml of liquid.

• A food is described as saturated fat-free if it has less than 0.1g of saturates per 100g or 100ml.

So, should I do my best to avoid fat?

Fat is required by the body. So long as not too much of it is eaten as part of a balanced diet regular exercise is undertaken, it does not pose a health risk.

Source: NHS Choices