Good fat bad fat

| 5 May 2020
minute reading time
Good fat bad fat

People are confused – bad science and poor journalism don’t help our understanding of fat, lumping the good and the bad in the same basket. Many people fear all types of fat, worrying that it’s always bad for our health and that it causes unwanted weight gain. But not all fat is bad…

Fat is essential for health and plays many roles in the body, from helping us to absorb vitamins A, D, E and K, to building the membrane of each of our cells. It also protects our vital organs by providing padding around them, insulates our bodies and provides us with energy.

Saturated fat

One fat we don’t need, however, is saturated fat as our bodies can make all we need – you don’t need any saturated fat at all in your diet. Diets high in saturated fat increase the risk of obesity, high blood cholesterol, heart disease, stroke, type 2 diabetes and some cancers. In fact, saturated fat raises blood cholesterol even more than cholesterol in foods, such as eggs for example.

The main sources of saturated fat are animal products – meat, eggs, dairy, pies, pastries, processed foods, fatty spreads and coconut oil and palm fat. Man-made trans fats are much rarer in foods now than they used to be, once it became clear how damaging they are to our health. We have no need for them and they increase the risk of heart disease and stroke.

Trans fat

Trans fats are twice as bad as saturated fat for blood cholesterol!  Low levels of trans fats are found naturally in dairy products, lamb and beef fat but they can also be found in some processed foods, such as biscuits, cakes, pastry and shortening as a result of manufacturers partially hydrogenating unsaturated vegetable oils. This converts them into solid or semi-solid states that increase the shelf life of these processed foods but does your health no favours – it’s wise to check the ingredients list. To reduce your trans fat intake, avoid all vegetable oil and margarine that list partially hydrogenated oil on the ingredient list.

Polyunsaturated fat

But not all fats are bad, and some polyunsaturated fats are essential in the diet as the body cannot produce them: linoleic acid (LA) is an omega-6 fat found in seeds, nuts, corn and soya oils and can be converted into other important omega-6 fatty acids in the body.


Alpha-linolenic acid (ALA) is an omega-3 essential fat that can be obtained from flaxseed/linseed (the richest source), walnuts, hempseed, rapeseed oil and soya beans. The body converts ALA to the longer-chain omega-3s EPA and DHA, which are required for healthy brain function.

Fishy pollutants

Oily fish are a source of EPA and DHA, which they get from eating algae naturally rich in omega-3s. However, all the world’s oceans are polluted so they also contain toxins such as mercury, polychlorinated biphenyls (PCBs) and dioxins. Fear not, you can get your omega-3s from the same place as the fish – algae. Vegan algae-based EPA and DHA supplements are available online and in health shops. The algae for these are usually grown in controlled conditions away from the sea so it doesn’t impact on marine ecosystems or deprive fish of their natural food. The bonus of algae supplements is that toxin levels are virtually non-existent, unlike in fish oil supplements.

Monounsaturated fats, including omega-7 and omega-9 fatty acids, are not classed as essential as the body can make them from other unsaturated fats. Good sources include olive oil, peanut oil, rapeseed oil, avocados and most nuts.


Some people get confused about cholesterol because it is essential for our health so it is assumed that we need it in our diet. Not true – the body produces its own cholesterol. Because animals also naturally produce their own cholesterol, it follows that animal products contain it. Plant-based foods, including every type of fruit and vegetable, pulses (peas, beans and lentils), wholegrains, nuts and seeds and even avocados are all completely cholesterol-free.

Cholesterol has to be transported to and from the cells by special carrier molecules called lipoproteins. Two types of lipoprotein are often mentioned in connection with cholesterol: low-density lipoprotein (LDL) and high-density lipoprotein (HDL).
Too much LDL in the blood can lead to the build-up of fatty plaques that can block the arteries, reducing blood flow to the heart and brain.  For this reason, LDL is often called ‘bad’ cholesterol.

HDL carries cholesterol away from the arteries and back to the liver where it is eliminated from the body and high HDL levels seems to protect against heart disease. It follows that HDL cholesterol is referred to as ‘good’ cholesterol.

Weight gain

We gain weight when we take in more energy or calories, than we need. They can come from fat, protein or carbohydrate. Protein and carbohydrate both provide four calories per gram whereas fat provides nine per gram. So, when eating the same amount of protein, carbohydrate or fat, you will always get more calories from the fat. It is not, however, a reason to avoid monounsaturated and polyunsaturated fats – just to eat them in moderation.

Go nuts! 

Many studies have found that some high-fat foods, such as nuts, can actually help prevent weight gain and even encourage weight loss. One study found that those who consumed nuts at least two times per week were 30 per cent less likely to gain weight (5 kg or more) in comparison with those who rarely ate nuts. This may be because nuts can reduce hunger and make you feel full for longer. They also contain fibre, so some of the fat is not absorbed and is carried into the bowel along with the fibre.

A varied vegan diet

You should be able to get all healthy good fats you need from eating a varied, vegan diet including ground flaxseed, hempseed, rapeseed oil for cooking and some nuts – especially walnuts – and seeds.

Having a diet high in omega-3s may help protect against heart disease and stroke, inflammatory diseases and neurodegenerative diseases, such as Alzheimer’s. To reduce your intake of saturated fat, cut out all animal foods and limit processed foods. Swap that beef steak for a tofu steak and replace chicken with chickpeas. Never cook with lard – olive oil is good for cooking and flaxseed oil for dressings. Add a small handful of nuts and seeds to your daily diet.

Avoiding animal foods rich in saturated fat, while including some foods containing unsaturated fat, such as avocados, nuts, seeds and a small amount of plant oil, is a simple and effective way to protect your health.

Find out more about fats here.

About the author
Dr. Justine Butler
Justine joined Viva! in 2005 after graduating from Bristol University with a PhD in molecular biology. After working as a campaigner, then researcher and writer, she is now Viva!’s head of research and her work focuses on animals, the environment and health. Justine’s scientific training helps her research and write both in-depth scientific reports, such as White Lies and the Meat Report, as well as easy-to-read factsheets and myth-busting articles for consumer magazines and updates on the latest research. Justine also recently wrote the Vegan for the Planet guide for Viva!’s Vegan Now campaign.

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