Good fats and bad fats explained

Four Types Of Fat | What Are ‘Healthy Fats’ | Benefits Of Unsaturated Fat | Are Saturated Fats Bad? | How Much Saturated Fat Per Day? | Are Trans Fats Bad? | Before Or After Workout

Page last updated: 30th November 2023

It wasn’t so long ago that fat was the greatest enemy of the fitness magazines, pundits, and health aficionados of the world. Until recently, it was believed a touch too much fat in your diet could spell disaster.

More recently though, it’s become widely known that fat is actually an essential macronutrient and plays a vital role in healthy hormone production[1].

Are all fats created equal? Are some genuinely good and some genuinely bad? And just how much is “too much”?

Let’s take a look.

The Four Types Of Dietary Fat: What’s The Difference?

Before we go on to explain ‘good’ and ‘bad’ fats in more detail, it’s important to understand what the different types of dietary fat are:

1. Saturated fat: typically found in animal products such as meat, dairy, and certain tropical oils like coconut and palm oil. Saturated fats have historically been considered to be ‘bad’ fats that lead to an increased risk of heart disease. However, more recent research has led to some reevaluation of the potential effects and saturated fat is now shedding its negative reputation. 
2. Monounsaturated fat: found in foods like olive oil, avocados, nuts and seeds, monounsaturated fats are generally considered ‘good’ - they’re heart-healthy and may improve cholesterol levels. 
3. Polyunsaturated fat: there are two types of this fat: omega 3 fatty acids, which are found in foods like fatty fish, flaxseeds, chia seeds and walnuts, and omega 6 fatty acids, which are found in oils such as soybean oil, corn oil and sunflower oil. Both of these fatty acids play important roles in maintaining overall health and are also considered to be ‘good’ fats. 
4. Trans fat: this is usually an artificial type of fat, created through a process called hydrogenation and found in some processed and packaged foods. This is definitely considered a ‘bad’ fat, which is linked to an increased risk of heart disease, and it's recommended to avoid this dietary fat where possible. 

What Is Meant By The Term ‘Healthy Fats’?

The term ‘healthy fats’ (or ‘good fats’) typically refers to unsaturated fats, which are considered beneficial for health when eaten in moderation as part of a balanced diet. In fact, they’re an essential part of a well-rounded and nutritious diet, as they provide energy, support cell structure and aid in the absorption of fat-soluble vitamins (A,D,E and K). They can also contribute to heart health by helping to keep your cholesterol levels in check and reducing the risk of cardiovascular disease. 

Examples of healthy fats include: 

• Avocados
• Olive oil
• Nuts (like almonds, peanuts and cashews)
• Seeds (such as pumpkin, sesame, chia and flax seeds)
• Fatty fish (such as salmon, mackerel and trout)

What Are The Benefits Of Unsaturated Fats?

While saturated fats may deserve the bad reputation they’ve garnered, the evidence is pretty conclusive when it comes to the health benefits of unsaturated fat (natural fat which remains liquid at room temperature, e.g. olive oil).

A 2016 Harvard study found that while mortality increased as saturated fat intake did (as compared to the same number of calories from carbs), it actually decreased – significantly – as unsaturated fat intake increased (again, compared to the same number of calories from carbs).

The decrease in overall mortality from a high unsaturated fat diet was striking, ranging from an 11% to a 19% lower overall risk, as compared to the carbs[2].

Unsaturated fats are further divided between monounsaturated fat (e.g. olive oil), and polyunsaturated fat (e.g. fatty fish, vegetable oils).

Monounsaturated fats are generally stable when cooking at high temperatures, and research suggests they may have a variety of incredible health benefits – like helping to prevent coronary heart disease[3].

The two sub-categories of polyunsaturated fat, omega 3 fatty acids and omega 6 fatty acids are more volatile and prone to damage and rancidity than monounsaturated fats (and as such, are less ideal for cooking). Omega 3 fatty acids are known to reduce inflammation in the body and help with a wide range of health conditions, including diabetes[4].

Omega 6 fatty acids are needed by the body too, but are typically over-abundant in modern Western diets due to a variety of factors (such as cattle being fed grain as opposed to grass). Evidence suggests that having too many omega 6 fatty acids in your diet can cause inflammation in the body[5], so it’s important to focus on getting sufficient omega 3’s in to even out the ratio[6].

Unlike with other macronutrient types, overall fat intake is generally not covered in national dietary guidelines. The key is to not exceed the suggestions for saturated fat intake, and to have unsaturated fats be the majority of your fat intake.

Are Saturated Fats Bad For You?

Saturated fat, which is found in meat, animal products, and certain vegetable products such as coconut oil, is a naturally-occurring fat which remains solid at room temperature.

During the height of the anti-fat movement of past decades, saturated fat was typically seen as the big baddie – the type of fat assumed to give you heart disease, cancer, and various other lethal ailments.

The initial fear of saturated fat was largely based on observational studies carried out in the 50’s, specifically Ancel Keys’ “Seven Countries Study”, in which diets high in saturated fat were correlated with populations at particular risk of heart disease[7].

Keys hypothesised that saturated fat was a leading cause of heart disease. The lab research, on the other hand, doesn’t offer such a clear-cut picture. In fact, large numbers of studies find no such correlation between saturated fat intake and heart disease[8].

Many recent studies go so far as to show the opposite[9] - for example, a 2016 study from the University of Bergen found evidence that dietary intake of saturated fat might actually improve blood pressure, among other health variables, while at the same time not increasing the risk of heart disease[10]. This was supported by a 2021 study of nearly 10,000 women which concluded that consuming saturated fat didn’t increase the risk of heart disease or death, and in fact may be linked to a lowering risk of other conditions, including obesity, type 2 diabetes and high blood pressure. 

However, the World Health Organisations recent guidelines, based on evidence from reviews of controlled trials and observational studies, still note that ‘lowering saturated fatty acids reduces low-density lipoprotein cholesterol and cardiovascular disease risk and may be associated with reduced risk of all-cause mortality and coronary heart disease’.[11]

So... are saturated fats bad for you? It seems the jury’s still out. Research seems to show that while they’re not as bad as once thought, it is still  worth keeping an eye on your intake and focusing primarily on consuming unsaturated fats instead.

How Much Saturated Fat Can You Have Per Day?

Public Health Britain suggests that the average man should eat only around 31g of saturated fat per day, while the average woman should eat only 24g per day[12].

Meanwhile, the World Health Organisation (WHO) recommends that adults and children keep saturated fatty acid intake at a maximum of 10% of total energy intake[13].

What Are Trans Fats And Are They Bad For You?

Trans fats are mainly found in hydrogenated oils that are included in some processed and packaged foods and are most commonly used to enhance the shelf like and texture of certain foods. 

They are typically found in fast food, cakes, margarines, vegetable oils, doughnuts and pastries, although many producers have agreed to reduce or completely remove the use of trans fats in their food. Although small amounts of trans fats can also be found in some animal products, these are not as strongly associated with adverse health effects as artificial trans fats. 

Trans fats have been linked to an increased risk of heart disease and raised LDL (low-density lipoprotein) cholesterol (often referred to as ‘bad’ cholesterol), while at the same time lowering HDL (high-density lipoprotein) cholesterol (considered to be ‘good’ cholesterol). This can contribute to the development of atherosclerosis and cardiovascular disease. 

These health risks mean many food manufacturers and restaurants have reduced--or eliminated--the use of trans fats in their produce. Despite countries like Denmark, Switzerland, Austria and some US states including New York and California banning trans fats, the UK has yet to do so[14].  

In summary, trans fats are universally considered bad for you, and it’s recommended you avoid or minimise consuming them whenever possible.

Should You Eat Fats Before Or After Your Workout?

We cover the best eating habits to fuel and recover from your workouts in our thorough guide to pre, during and post workout nutrition. In short, you can choose to eat a moderate amount of healthy fats ahead of your workout, and/or as part of a post-exercise recovery meal. 

Before workout:

• Consuming a moderate amount of healthy fats before a workout can provide a slow-release source of energy. Fats take longer to digest compared to carbohydrates, which can help sustain energy levels during longer, endurance-type activities.
  
  
• Opt for easily digestible fats, such as those found in nuts, seeds, or a small amount of nut butter, rather than heavy or greasy meals.

After workout:

• Post-workout nutrition is crucial for recovery, and it typically focuses on replenishing glycogen stores and providing protein for muscle repair.
  
  
• While the emphasis is often on carbohydrates and protein, including some healthy fats in your post-workout meal can contribute to a well-balanced recovery meal.

In summary

The ‘Good’: Unsaturated fats (i.e. polyunsaturated and monounsaturated fatty acids) are definitely good for you, and should be included in any well rounded, nutritious diet. 

The ‘Bad’: Trans fats have been proven to have adverse health effects, so are best avoided as much as possible. 

The ‘Middle Ground’: Research and advice is mixed on saturated fats, but general health recommendations are that these can be included in your diet, but should be limited. 

For more advice, head over to our diet and nutrition hub which is packed full of informative guides to maintaining a healthy diet. The best results for overall health and wellbeing come from combining considered, balanced eating with an exercise plan that works for you. Become a PureGym member and you can make the most of our high quality fitness equipment, and can even book in for sessions with our expert personal trainers who will be able to advise you on the best meal and workout plans for you.