Dietary Fat: Types, Functions and Healthier Choices

Fat is an essential macronutrient that the body needs to function properly. Although dietary fat is sometimes viewed negatively, eating a suitable amount of the right types of fat is an important part of a healthy, balanced diet.

Fat provides energy, protects the organs, supports healthy cells and helps the body absorb certain vitamins.

Why Does the Body Need Fat?

Dietary fat performs several important functions within the body. It helps to:

• Provide and store energy
• Protect internal organs
• Insulate the body
• Support healthy cell function
• Produce certain hormones
• Supply essential fatty acids
• Absorb fat-soluble vitamins

Fat provides approximately nine calories per gram, making it the most concentrated source of dietary energy. Carbohydrates and protein each provide approximately four calories per gram.

Because fat is energy-dense, regularly consuming more energy than the body needs can contribute to weight gain. Being overweight can increase the risk of several long-term health conditions.

Fat and the Absorption of Vitamins

Fat helps the body absorb the fat-soluble vitamins A, D, E and K.

These vitamins perform several important functions:

• Vitamin A supports normal vision, immunity and healthy skin.
• Vitamin D supports healthy bones, teeth and muscles.
• Vitamin E helps protect cells from oxidative damage.
• Vitamin K contributes to normal blood clotting and bone health.

What Are the Different Types of Fat?

Dietary fats can be divided into several types. The two main groups are:

• Saturated fats
• Unsaturated fats

Most foods contain a combination of different fats, but one type may be present in a greater proportion.

What Is Saturated Fat?

Saturated fat is commonly found in foods such as:

• Butter
• Lard and ghee
• Cream
• Hard cheese
• Full-fat dairy products
• Fatty cuts of meat
• Sausages and meat pies
• Cakes, biscuits and pastries
• Chocolate
• Some processed foods and ready meals
• Coconut oil
• Palm oil

Eating too much saturated fat can raise harmful cholesterol levels, increasing the risk of heart and circulatory disease.

Healthier eating guidance recommends reducing saturated fat and replacing some of it with unsaturated fat rather than replacing it with foods high in sugar or refined carbohydrates.

Recommended Saturated Fat Limits

As a general guide:

• The average man should consume no more than 30g of saturated fat a day.
• The average woman should consume no more than 20g of saturated fat a day.
• Children should consume less, with the amount depending on their age.

People with heart disease or an increased risk of cardiovascular disease may receive different individual advice from a qualified healthcare professional.

What Is Unsaturated Fat?

Unsaturated fats are generally considered a healthier choice when they replace saturated fats and are consumed in appropriate amounts.

The two main types of unsaturated fat are:

• Monounsaturated fat
• Polyunsaturated fat

All fats are high in energy, so unsaturated fats should still be eaten in moderation.

Monounsaturated Fats

Monounsaturated fats are found in foods including:

• Olive oil
• Rapeseed oil
• Avocados
• Almonds
• Peanuts
• Cashew nuts
• Nut butters
• Some seeds

Replacing foods high in saturated fat with foods containing monounsaturated fat can help support healthy cholesterol levels and reduce the risk of heart and circulatory disease.

Polyunsaturated Fats

Polyunsaturated fats are found in foods including:

• Sunflower oil
• Corn oil
• Soya oil
• Rapeseed oil
• Nuts
• Seeds
• Oily fish

Polyunsaturated fats include the essential fatty acids omega-3 and omega-6. The body cannot make enough of certain essential fatty acids, so they must be obtained through the diet.

What Are Omega-3 Fatty Acids?

Omega-3 fatty acids support normal body functions and are associated with heart health. Oily fish is a particularly valuable source of long-chain omega-3 fats.

Good sources of omega-3 include:

• Salmon
• Mackerel
• Herring
• Sardines
• Pilchards
• Trout
• Kippers

Healthy eating guidance recommends eating at least two portions of fish each week, including one portion of oily fish.

Some people, including those who are pregnant, breastfeeding or planning a pregnancy, are advised to limit the amount of certain oily fish they eat. Current NHS guidance should be followed.

Plant-Based Sources of Omega-3

People who do not eat fish can obtain omega-3 fats from plant-based foods including:

• Walnuts
• Flaxseeds or linseeds
• Flaxseed or linseed oil
• Chia seeds
• Rapeseed oil
• Soya products
• Omega-3-enriched eggs

Plant foods generally contain a different form of omega-3 from that found in oily fish, and the body converts only a limited amount into the long-chain forms used by the body.

What Are Omega-6 Fatty Acids?

Omega-6 fatty acids are another type of polyunsaturated fat. They are found in foods such as:

• Sunflower oil
• Corn oil
• Soya oil
• Rapeseed oil
• Walnuts
• Almonds
• Cashew nuts
• Seeds

When used to replace saturated fats as part of a balanced diet, polyunsaturated fats can help reduce harmful cholesterol levels.

What Is Cholesterol?

Cholesterol is a waxy substance that is produced naturally by the body. It is needed to make cell membranes, vitamin D and certain hormones.

Cholesterol travels through the blood in particles called lipoproteins. Although cholesterol is necessary, unhealthy levels can increase the risk of heart attack, stroke and other circulatory conditions.

LDL Cholesterol

Low-density lipoprotein, or LDL cholesterol, is sometimes called “bad” cholesterol. High levels can contribute to the build-up of fatty material inside the arteries.

This build-up can narrow the arteries and restrict blood flow, increasing the risk of heart and circulatory disease.

HDL Cholesterol

High-density lipoprotein, or HDL cholesterol, is sometimes called “good” cholesterol. It helps carry cholesterol away from the arteries and back to the liver, where it can be processed and removed from the body.

Cholesterol results should be considered as a whole because LDL, HDL, non-HDL cholesterol, triglycerides and other health factors can all affect cardiovascular risk.

Dietary Cholesterol and Blood Cholesterol

For most people, saturated fat has a greater effect on blood cholesterol than the cholesterol naturally present in foods such as eggs.

This is why healthy eating guidance focuses particularly on reducing saturated fat and replacing it with unsaturated fat.

Visible and Hidden Fats

Dietary fat may be described as visible or hidden fat.

Visible Fats

Visible fats are easy to recognise and include:

• Butter and spreads
• Cooking oils
• Cream
• Fat on meat
• Salad dressings

Hidden Fats

Hidden fats are present in foods where the fat may not be immediately obvious. Examples include:

• Cakes
• Biscuits
• Pastries
• Chocolate
• Sauces
• Pies
• Processed meat products
• Takeaway foods
• Some ready meals

Checking the nutrition information and front-of-pack traffic-light label can help identify foods that are high in total fat or saturated fat.

How Cooking Methods Affect Fat Content

The way food is prepared and cooked can significantly affect how much fat it contains.

Cooking methods that generally require little or no added fat include:

• Steaming
• Grilling
• Baking
• Poaching
• Boiling
• Microwaving
• Casseroling
• Air frying with little or no added oil

Deep frying and some forms of pan frying can add considerably more fat to food.

Practical Ways to Choose Healthier Fats

To improve the balance of fats in the diet:

• Replace butter, lard or ghee with small amounts of unsaturated oils or spreads
• Choose leaner cuts of meat and remove visible fat
• Remove the skin from poultry where appropriate
• Eat oily fish regularly within current guidance
• Choose unsalted nuts and seeds in moderate portions
• Limit cakes, biscuits, pastries and processed meat products
• Use grilling, steaming, baking or poaching instead of deep frying
• Check food labels for saturated fat
• Remember that all fats are high in calories

Fat as Part of a Balanced Diet

Fat is an essential part of a healthy diet, but the amount and type of fat matter.

Choosing more unsaturated fats, reducing saturated fat and using cooking methods that require less added fat can support healthy cholesterol levels, cardiovascular health and long-term wellbeing.