Fat: Good, Bad, or Both?


by Alejandra "Alex" Ruani — Get free science updates here.

When you look at a food label, you’ll notice that fat is the first macronutrient to appear on the list, such as in the UK label below:    

With high rates of obesity across much of the world, fat has been put in the spotlight as one of the causative agents.

But is fat as bad as all that?

First, we need to discover what we use fat for in the body.

The diagram below will help you to understand the critical roles that fat has in our body:

You are already probably aware that fat can be found in a variety of foods. We typically think of fats as being found in oils, processed foods, fatty meats, and a number of dairy foods. But fat is also found in avocados, olives, nuts, and seeds.

Look at the amount of fat in 100 grams of avocado compared to 100 grams of bacon rashers:

You can see that bacon contains significantly more total fat per 100g. But the total fat isn’t the full story.

Just like with carbohydrates, there are different types of fats and they are not created equal when it comes to nutrition.

Do you see the 4 different fats listed on this US food label?

They are:

  • Saturated fat
  • Trans fat
  • Monounsaturated fat
  • Polyunsaturated fat

 

Additionally, the ‘Total Fat’ on the label accounts for all the individual fats counted as a whole.

Eagle-eyed readers amongst you might notice that the individual components of fat on this label actually only add up to 5.5g! That’s because these measurements are rounded to the nearest 0.5g.

The differences between the fats are based on their chemical structure (how the carbons and hydrogens are put together).

We won’t go into all the chemical compositions of these fats here, but let’s learn about a few of the most important fats in our diets.

Polyunsaturated fats consist of both omega 3 and 6 fatty acids.

The two main omega 3 and 6 fatty acids are considered to be essential.

This is because the body can make other fats.

But it can’t make linoleic acid (an omega 6) or alpha-linolenic acid (an omega 3). So, these need to be obtained through the diet.

Our modern diets tend to be high in omega 6 (primarily from vegetable oils in spreads and processed foods), but often low in omega 3.

Of special note is oily fish, which contains high levels of EPA and DHA. These are a type of omega 3 fatty acid, but ones that are only produced in small amounts in our bodies from alpha-linolenic acid. Therefore, it may be beneficial to obtain these directly!

Saturated fats are generally hard at room temperature. They are found mainly in animal products such as meat fat, egg yolk, and dairy fats of cream, butter, milk, and cheese and plant sources such as palm and coconut oil. They are non-essential, as the body can synthesise them in the liver.

There is some debate about the health effects of saturated fats, but most countries and researchers generally agree that they may be able to cause harm when consumed in moderate to high quantities.

Trans fats are what are normally considered “bad fats”. They are artificially created from vegetable oils and have been shown to raise your bad (LDL) cholesterol levels and lower your good (HDL) cholesterol levels, thus increasing your risk of developing heart disease and stroke.

In Europe, trans fats are not specifically listed on nutritional labels.

However, in the US, they usually are.

You can see these differences in the labels below:

Fortunately, most manufacturers have taken steps to dramatically reduce the amount of trans fats in products, and some (such as Denmark) have imposed a total ban.

Government guidelines recommend that less than 11% of your total energy (caloric) intake should come from saturated fats. It is also suggested that the best option is not to simply remove saturated fat from the diet but aim to replace it with mono- and polyunsaturated fats.

Also worth bearing in mind is that fat contains 9 calories per gram, compared to protein and carbohydrates which contain 4 calories per gram. This means that high fat intakes (even healthy fats) may also come with a lot of calories attached!

But what can fat do to our appetites? Can it fill us up and stop us from eating, or does it encourage us to go on a food binge? Want to find out the answer? Then click here.

 

 

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The-Health-Sciences-Academy-Alejandra-Ruani-small1-right Alejandra "Alex" Ruani leads the research division at The Health Sciences Academy, where she and her team make sense of complex scientific literature and translate it into easy-to-understand practical concepts for their students. She is a Harvard-trained scientist and UCL doctoral researcher who specialises in cravings and appetite neurobiology, nutrition biochemistry, and nutrigenomics. Besides investigating and teaching the latest advances in health and nutrition science, Alex makes it easier to be smarter with her free Science Catch-ups.

Connect with Alex via email.


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