Why do you need fat?

Fat is usually thought of as a bad thing. But your body does actually need some. For one thing, it’s a valuable source of energy – 1g of fat provides nine calories per gram, compared with four calories for protein and less than four for carbohydrates. You also need fat to absorb certain vitamins that are important for your health – such as vitamins A, D, E and K.

Fat is made up of individual ‘building blocks’ of fatty acids. Some of these fatty acids have vital functions in your body, and you have to get them from your diet as your body can’t make them. These are known as essential fatty acids and include omega-3 and omega-6. The essential fatty acids are important as they are used to make the outer layer (membrane) of the cells in your body and are also involved in the production of certain substances that control chemical reactions inside your cells.

The good and the bad…

Although it’s clear you need some fat in your diet, it’s all too obvious what can happen if you eat too much. Fat is the richest form of energy in your diet, which means it’s easy to eat more than you can burn off through activity and you can gain weight. The rise in obesity levels is often blamed on eating too much fatty food. However, it’s a bit more complicated than that. For instance, perhaps surprisingly, the average intake of fat in the UK isn’t far off the recommended level. And as a population, people are eating less fat than 25 years ago. So why are people getting fatter?

The problem seems to be not the total amount of fat we eat, but the types of fat. Fats are classified as either saturated, monounsaturated or polyunsaturated, depending on the chemical structure of the fatty acids they contain. There are also trans-fats – a type of fat that is mainly made artificially in the processing of vegetable oils to make margarines.

Saturated and trans-fats are largely the 'bad' types – the ones that are harmful for your health and can increase cholesterol levels and lead to heart disease. Trans-fats are thought to be particularly unhealthy as they increase bad forms of cholesterol (low-density lipoprotein) while also lowering good forms (high-density lipoprotein). However, since their harmful effects have been exposed, the food industry in the UK has done a lot to cut these fats out of processed foods; so fortunately, most of us don’t get that much anyway. Saturated fats are the ones that cause the most problems, as in general, people eat far too much of them. In the UK, about 13 percent of people’s energy intake currently comes from saturated fats, when the recommended level is 11 percent.

Monounsaturated and polyunsaturated fats, meanwhile, are actually good for you. And yet, most people don’t eat enough of these types of fat. Unsaturated fats help to lower cholesterol and also provide you with the essential fatty acids that your body needs.

Getting the right amounts

So what food do you need to eat to get the right balance of fats in your diet?

Saturated fat

Try to limit the amount of saturated fats in your diet. They are usually solid at room temperature and often come from animals.

Foods high in saturated fats include:

  • fatty meat and meat products
  • dairy products – such as butter, cheese and cream
  • pastries
  • cakes and biscuits
  • chocolate
  • coconut oil and palm oil

The average man should have no more than 30g of saturated fat a day, and the average woman no more than 20g. What does this mean in practice? A typical 30g portion of cheddar cheese contains about 7g saturated fat if you tuck into a couple of sausages or a cheeseburger you could eat about 10g. It’s not hard to reach your daily limit.

You don’t need to record the amount of fat in every single food you eat, but it’s a good idea to check on food labels for those that contain a lot of saturated fat. That way you can start to recognise what these are and try to cut down on them. A high amount of saturated fat is anything over 5g of saturated fat per 100g, whereas a low amount is considered to fall under 1.5g of saturated fat per 100g.

Unsaturated fat

Unsaturated fats – which include monounsaturated and polyunsaturated fats – are the type of fats to aim to eat instead of saturated fats. They are generally liquid at room temperature and often come from plants.

Good sources of unsaturated fats include:

  • sunflower, rapeseed, olive and vegetable oils, and spreads made from these oils (so long as they have not been hydrogenated)
  • avocados
  • nuts and seeds
  • oily fish, such as mackerel, salmon or trout – these are a particularly good source of omega-3

Fat-free tips

Try these simple tips to get the right balance of fats in your diet.

  • Watch your portion sizes – if you’re a fan of bacon sandwiches for breakfast, have one or less rasher in your sandwich; if you love your cheese, grate it to make it go further; and when you do fancy a cake or biscuit, try to stick to one!
  • Swap your weekend fry-up for smoked mackerel for breakfast – you’ll cut down on your saturated fat.
  • Go for leaner cuts of meat, or opt for chicken or fish and keep red meat to a minimum.
  • Save butter for an occasional treat and try reduced-fat spreads instead.
  • Choose tomato-based sauces over creamy or cheesy ones in pasta dishes and curries.
  • Grill or bake your food rather than fry it.
  • If you’ve got the munchies, snack on fruit, toast with low-fat spread or a handful of nuts, rather than cakes and biscuits.