Good fats and bad fats

Good fats and bad fats

Team ErbologyErbology

Can you tell your saturated fats from your trans fats? Your monounsaturated from your polyunsaturated fats? The wisdom about good fats and bad fats is often lost in a sea of unhelpful jargon, leaving many of us unsure of what we should be eating. In this article, we’re going to break down exactly which types of fat count as ‘good for you’ and why, and which types you should approach with caution.

April 27, 2022 4:44 pm

Fat: a misunderstood nutrient?

If you are above the age of twenty or so, you’ll probably have some fixed ideas about dietary fat.

The first thing to say is that for many years, we were told that fat was bad for us, and that ‘eating fat makes you fat’.

Later, we learned that some types of fat were particularly bad for us. Top of the naughty list were saturated fats.

Back when we were kids, saturate-packed butter was banished from the house in favour of olive oil spreads and margarines. Then came the news that some margarines contained ‘trans fats’ which were even worse for us.

Out went the margarine, and back came the butter; but then we began to hear about how healthy plant oils such as olive oil were for us.

Butter was relegated once more in favour of this Mediterranean staple, but then news arrives that heavily processed olive oils have lost many of nutrients we thought they had.

It’s no wonder that a lot of us are confused.


butter, a bad fat

Is fat really bad for you?

The truth is, scientific opinion about dietary fats and their impact on our health has changed quite a bit in recent years.

Many of us have come to accept that not all fats are bad. In fact, some types of dietary fat can actually be good for us.

The trouble we have now is differentiating between the different kinds and how healthy they are.

The debate which continues over whether fats are good or bad for you centres around their link to your cholesterol levels. Some fats seem to increase your levels of ‘bad’ LDL cholesterol and reduce your ‘good’ HDL cholesterol, and as we know, having a poor balance of these can lead to disease.

It’s also worth saying that all fat is very rich in calories. Eating too much of any type of fat can push you over the calories you need to maintain a healthy weight, and can lead to weight gain.

What are the different types of fat?

There are three major groups of fats, and within these there are subdivisions. All fats contain a mixture of saturated and unsaturated fats, but they are categorised by whichever type of fat is dominant in that particular product.

Saturated fats

The first group is the saturated fats. These are most commonly associated with animal products like meat and cheese, but they can also be found in plant-based foods like coconut oil. They tend to be solid at room temperature.

What is a saturated fat?

They’re defined by their molecular structure. If we can dust off our high school chemistry text books for a moment, all fats are made of chains of carbon atoms. Some of these carbon atoms are connected by a single bond, and some have a double bond.

If there’s a double bond, it can be broken to form a single bond with another hydrogen atom. At this point, it’s ‘saturated’; the remaining place available for hydrogen atoms to join has been filled.(1)

Some common types of saturated fats are lauric acid and myristic acid (found in coconut and palm oils) and palmitic acid and stearic acid (found in beef mince, butter and eggs).

As we’ll discuss below, these fats are generally thought to be ‘unhealthy’, although there is a bit of controversy around their health effects.

The verdict: Bad fat (with some caveats)

For years and years, saturated fat was thought to be very bad for you.

The logic went as follows: in the 1950s, heart disease had become one of the leading causes of death in the Western world. Heart disease can be caused by a build-up of atherosclerotic plaques (the stuff that clogs your arteries). A large proportion of these plaques is cholesterol, therefore foods which raise your cholesterol levels (such as saturated fats) must increase your risk of heart disease.(2)(3)

It’s at this point that everyone starts worrying about their cholesterol!

Saturated fats being bad for your health was the accepted wisdom for many years, however recent scientific studies have begun to challenge that assumption.

In a nutshell, some scientific studies have suggested a strong link between consuming saturated fat and your risk of heart disease, while others have found no link at all.(4)

Many scientists have reasoned that the discrepancy comes from the source of the saturated fat, its molecular structure, and what it ends up being replaced with in the diet.(4)

However, it seems likely based on the evidence that replacing some of the saturated fat in our diets with unsaturated fats (particularly polyunsaturated fats, or PUFAs) would help reduce our risk of heart disease.(4)(5)

The general scientific advice is to keep your consumption of saturated fats as low as you can.

Related reading


a cheese platter with bad fats

Foods to look out for with saturated fat

If you’re keen to reduce your intake of saturated fat, avoid eating fatty cuts of (especially red) meat and processed meats. It’s also wise to cut down your consumption of high fat dairy foods such as cheese.

One reason many of us are eating too many saturated fats is that they’re very commonly found in processed foods, and we don’t always check the label.

It’s best to cook your own food, so you know exactly what’s in it. But if that’s impractical, make sure you look at the nutritional information on the label.

In the UK, saturated fat must be listed and colour coded on the product label. Any food which contains more than 5g saturated fat is considered to be ‘high’ in saturated fats.

Men should aim to eat no more than 30g saturated fat per day, while the count for women is 20g.(6)

"It’s best to cook your own food, so you know exactly what’s in it. But if that’s impractical, make sure you look at the nutritional information on the label."

hemp seed oil toast

Unsaturated fats

What is an unsaturated fat?

Unsaturated fats have retained their double (or triple) bonds. They tend to be liquid at room temperature.

Within this category are two main subgroups: monounsaturated fats and polyunsaturated fats. Monounsaturated fats have one double bond in each molecule, while polyunsaturated fats have several.(1)

Foods which contain predominantly monounsaturated fats include olive oil, avocados, almonds and pumpkin seeds. Omega-9 and omega-7 are also monounsaturated fatty acids.

Polyunsaturated fats are made up of omega-3 and omega-6 fatty acids. Sources of these include sunflower oil, linseeds, walnuts and fish.

These are called ‘essential fatty acids’ as we need them to perform key functions in the body, but can’t produce them ourselves. Thus, it’s ‘essential’ that we get them from our diet.

The verdict: Good fat

As you’ve probably guessed, these fats are broadly considered to be the healthy ones.

Monounsaturated fats are thought to reduce your levels of ‘bad’ LDL cholesterol.(1)

In cold-pressed oils, such as olive oil, they are combined with other healthy nutrients such as antioxidants and anti-inflammatories, meaning there are other reasons these oils may be good for our health beyond their fatty acid structure.

The polyunsaturated fats omega-6 and omega-3 are needed to maintain a healthy nervous system and cell membranes.

They are also both associated with benefits to your heart and cardiovascular health. Omega-3, for example, is likely to reduce sudden cardiac death, while higher intake of omega-6 is linked with a lower risk of heart disease, cancer and overall mortality.(1)

However, it’s important to get the right ratio of omega-6 to omega-3. In the West, we generally eat far too much omega-6 – which can also be found in processed vegetable oils = and not enough omega-3.

To get the best health effects, the ratio to aim for is between 1:1 and 4:1 (omega-6 to omega-3). Aim to get your omega-6 from cold-pressed vegetable oils rather than processed oils. This will make sure you’re getting a host of other healthy nutrients alongside your omega-6.


organic almonds

Foods to look our for with unsaturated fats

Stock up on good unsaturated fats by eating high-fat whole foods such as avocados, peanuts, and almonds.

You can find your omega-6 in sunflower oil, although most of us tend to get enough omega-6 from our normal diets.

When it comes to omega-3, you’ll often hear fish such as salmon and sardines listed as good sources. Indeed they are, but you can also get your omegas from the plant world, if you prefer.

Try hemp seed oil, which has a perfect ratio of omega-3 to omega-6 fatty acids (1:3). Alternatively, cold-pressed walnut and chia oils are also a source of omega-3.

Just be aware that omega-3 from plant sources is likely to be absorbed less effectively by your body than fish sources.


chia seed oil, a good fat

Trans fats

Counterintuitively, trans fats (currently thought to be the worst of all for your health) are also unsaturated fats. However, they are most definitely not good for you.

Animal products like meat and dairy contain a small amount of naturally occurring trans fats. But the ones we’re really worried about are those which are created artificially.

What are artificial (hydrogenated) trans fats?

Artificial trans fats are made when manufacturers add hydrogen to vegetable oils to turn them into a solid.

Why would anyone do this? Well, the process has allowed manufacturers to make products with a longer shelf life, a better texture and to make things like solid plant-based spreads from vegetable oils.

As a result they’re most commonly found in heavily processed foods.

The verdict: Really, really bad fat

Sadly, there is absolutely nothing to redeem artificial trans fats; they have no nutritional benefit whatsoever.

Quite the opposite: tans fats are linked with an increased risk of heart attack and heart disease.

However, there is some good news: many countries have now taken steps to ban or legally limit hydrogenated trans fats in food, including the US and Canada, Austria, Denmark and Sweden. (You can check your country’s status on the World Health Organisation’s list.)(3)

Surprisingly, the UK is not on the list, however according to the NHS, most people in the UK don’t eat too much trans fat. Most of us eat about half the recommended daily maximum.(8)


good fats and bad fats

Foods to look our for with trans fats

If you’re lucky enough to live in a nation which has banned trans fats, this is something you don’t really have to worry about. (One watch out: in the USA, the ban came into force in 2018, but some products made before then may still be circulating.)

If, however, trans fats are still allowed in your country, we highly recommend you carefully check the labels of the processed foods you eat to make sure they do not contain trans fats.

Be especially vigilant around margarines, vegetable oils and processed snacks like cakes, doughnuts and biscuits.

Some unscrupulous manufacturers have tried to dodge the bad reputation of trans fats by listing them as ‘mono and diglycerides of fatty acids’ on their ingredients lists, so watch out for those, too!(10)

While many manufacturers have acknowledged the need to get rid of trans fats from their products, there is currently no legal pressure to do so. In places where nutritional labelling isn’t required (such as fast food restaurants), trans fats are still relatively common. There’s also no way to tell if you’re eating them.

That said, lots of products such as margarines and plant-based spreads have been reformulated in recent years to remove most or all of the trans fats.

Read the label

Some products which contain trans fats don’t always make it obvious on the label.

Here are some other names for trans fats which you might come across on products you eat:

  • Mono and diglycerides of fatty acids
  • Shortening
  • Partially hydrogenated vegetable oil
  • Hydrogenated vegetable oil
  • Trans fatty acids

Guess I’d better stick to ‘low fat’ foods from now on?

If only it were so simple!

Firstly, as we’ve seen, not all fats are bad. Eating healthy unsaturated fats is beneficial for your health, so there’s no reason to avoid them.

However, most of the time, ‘low fat’ labelling applies to processed foods. There, you’re likely to be dealing with saturated or trans fats.

The best thing to do is to avoid eating lots of processed foods as far as you can. However, if you still want to eat processed foods but want to watch your saturated or trans fat intake, there’s something important you should know.

Often, when manufacturers take fat out of a product, they put something else in.

One of the most common culprits is sugar.

For example, low fat yoghurts are notorious for being loaded with added sugar, which. Is put into the yoghurt to improve the flavour once the fat has been removed.

Similarly, natural peanut butter should generally just contain peanuts (and possibly a bit of salt). However, reduced fat peanut butter often replaces the lost fat with sugar and corn syrup. This results in a product which is much worse for you than the original!

The confusion around fats

As we’ve seen, there are so many opinions surrounding dietary fat that it has become a really confusing part of trying to eat healthily.

While it’s good to know about all these things, sometimes it’s best to drill down to a simple conclusion you can take forward into your daily life with you.

When it comes to fat:

  • Too much fat of any kind leads to weight gain.
  • If it comes from a plant, and it has not been processed, it’s likely to be good for you.
  • If it is included in a mass-produced, processed product like a biscuit or cake, it’s likely to be bad for you.
  • There is some debate around saturated fat, but it’s always better to choose unsaturated fats if you can. Otherwise, make sure that only a small proportion of the fat you eat is saturated fat.
  • Avoid trans fat like the plague.

There you have it! Follow these golden rules and you’ll soon master the art of telling the good from the bad.

Related reading

Sign up to Erbology updates and get a surprise.

By subscribing you agree to our Terms and Privacy Policy.

Invite & Earn

Signup to start sharing your link