What are dietary fats?
Dietary fats are one of the three macronutrients. Of the three macronutrients, fats are the most energy dense.
While protein and carbohydrates each give us 17kj per gram, fats give us 37kj per gram; this is part of the reason why dietary fats are often blamed for excess body weight and obesity.
When we eat dietary fats, they are in a form called triglycerides. As the name suggests, a triglyceride is three fatty acids linked to a glycerol molecule. The fatty acids are links for carbon and hydrogen atoms, of varying lengths. One of the ways we classify dietary fats is by the chain length; for example, you may have heard of the term’ medium chain triglyceride’.
The fats we eat in our diet are usually long chain fatty acids. Both long chain and very-long chain fatty acids, once consumed and digested, are absorbed in our bloodstream, and released as energy into cells when required.
Short- and medium chain fatty acids are taken up by the liver and are stored there as energy. Apart from a small amount in milk fats, short chain fatty acids aren’t readily found in our diets; instead, they are made in our bodies.
Bacteria in our colon feed on the soluble fibre we consume, the fermentation process results in short chain fatty acids.
Here is a quick list of the carbons found in a link in each type of fatty acid:
- short-chain fatty acids: fewer than 6 carbons
- medium-chain fatty acids: 6–12 carbons
- long-chain fatty acids: 13–21 carbons
- very long-chain fatty acids: 22 or more carbons
Functions, actions, and benefits of fats
As we’ve just read above, fats are a dense source of energy, which our body can use as an energy source. For every gram of dietary fat, you will get twice the amount of energy than that of a gram of protein or carbohydrate!
But fats have a few more functions and benefits than just being a dense energy source, including:
- Brain function: Whilst glucose is the brain’s favoured choice for energy, fats are required to maintain brain health and can assist in mood.
- Vitamin absorption: Vitamins A, D, E and K are all what we call fat-soluble vitamins; that is, they need to be consumed with dietary fats to ensure their digestion and absorption.
- Hormone health: Fats are used as a building block in the form of cholesterol for many of our reproductive and steroid hormones. Without fats we wouldn’t be able to produce hormones such as progesterone, estrogen, and testosterone.
- Fullness and flavour: We all know this one! Dietary fats can make foods tasty and more pleasurable to eat and will also help to make a meal feel more filling.
- Protection: Fat that is being stored in the body is used as protection and insulation. Stored fat will help to keep us warm and will provide a protective layer around our organs.
Understanding fat saturation
Another way that dietary fats can be classed is by their’ saturation’.
You may be familiar with terms such as ‘polyunsaturated’ or ‘saturated’ fats. These terms refer to how many double bonds there are in a fatty acid chain, and therefore their stability.
You may recognise these terms:
- Monounsaturated fats
- Polyunsaturated fats
- Saturated fat
- Trans fats
Monounsaturated fats (MUFAs)
These fats are named as they have one double bond in their carbon chains. MUFAs are usually liquid at room temperature, think olive oil, and are heat-stable for cooking purposes.
In terms of health benefits, MUFAs have been shown to reduce CVD and diabetes. When compared to high carb diets, diets high in MUFAs have demonstrated the ability to lower blood pressure, serum triglycerides and blood glucose levels.
Foods with higher MUFA content may increase satiety and lead to reduce caloric intake.
MUFAs are found in most plant and animal foods, however, here are some MUFA rich foods; olive oil, olives, macadamia nuts, almonds, pecans, hazelnuts, pistachios, peanuts, avocados, pork, and beef.
Polyunsaturated fats (PUFAs)
Well known Omega-3 Fish Oils are part of the PUFA family. PUFAs have two or more double bonds in their fatty acid chains; it’s the location of the double bond that further subdivide this category.
Omega-3, Omega-6, Omega-9, they all have double bonds at different points in their chains. The double bonds help to make PUFAs more fluid and flexible than saturated fats, but it also makes them more susceptible to oxidization and going rancid.
Many people are aware of the benefits of Omega-3 PUFAs; they have been shown to reduce inflammation and decrease the risk of CVD and depression. Good sources of Omega-3 PUFAs are foods like oily fish and oily nuts, such as salmon, sardines, herring, mackerel, anchovies, chia seeds, flaxseed, and walnuts.
Omega-6 fats are very common in the diet; whilst we need these good fats in our diets to much can contribute to chronic inflammation, especially if you don’t have enough Omega-3 in your diet. Omega-6 is found in most plant and animal foods, especially the foods in the list of monounsaturated fats.
To maximize the benefit of Omega-3 foods, and limit the risk of inflammation caused by excess Omega-6, the ratio to aim for is a ratio of Omega-3-Omega-6 is 1:4-4:1 depending on your specific health needs.
Saturated and Trans fats
These two types of fats are often referred to as ‘bad fats’. Saturated fats are often used in cooking at high temperatures, like frying, as they are more stable. Most dietary trans fats are unnatural foods produced by adding hydrogen to unsaturated fats; thus, enabling them to function like a saturated fat.
Trans fats are often used as stabilisers to extend the shelf life of foods like crackers, margarine, and other spreads.
Eating saturated fats in moderation has been found to have a neutral effect on our health, except for medium chain fatty acids like coconut oil which may have a positive effect on metabolic health. Trans fats, however, are generally not good for our health.
Eating processed and refined foods containing trans fats has been linked to inflammation, impaired artery function and health, insulin resistance, dysfunction cholesterol levels, increased risk of CVD, and negative alterations in body composition. It’s best to aim for a diet with little or no trans fats.
Fat diet types
As you can see, it’s important to make sure you get enough of the good fats in your diet and try to limit saturated and trans fats.
The Australian Ministry for Health has advised there are currently no upper level limits on daily amounts of monounsaturated fats. There is a recommendation of the upper limit of 3000mg of Omega-3 for children through to adults.
So, aside from this how much dietary fat you consume will depend on your health and fitness goals. Let’s have a look at three times of dietary fat-based food philosophies.
Low fat diets are often touted as being a way to lose weight and improve body composition.
When considering a low-fat diet, it’s important to ensure you don’t replace the flavour for fat, with the flavour of sugar!
A diet comprising of 30%, or less, of fats is considered low fat. On a food or meal plan this may look like:
- 1,500 calories: about 50 grams of fat per day
- 2,000 calories: about 67 grams of fat per day
- 2,500 calories: about 83 grams of fat per day
Low Carb, High Fat (LCHF) or Keto
Ketogenic diets came into fad a few years ago, just before the plant-based/vegan movement came along. Keto and LCHF diets will have minimal carbohydrates, higher fat percentage and low to moderate protein intake (depending on the diet). A keto diet can be up to 75% dietary fats!
These diets can be useful in some health conditions, body composition, or for certain athletes.
Depending on the food or meal plan, fat consumption may look like:
- 1,500 calories: about 83–125 grams of fat per day.
- 2,000 calories: about 111–167 grams of fat per day.
- 2,500 calories: about 139–208 grams of fat per day.
The Mediterranean diet has often been prescribed for cardiovascular health and support. It is balanced, whole food diet full of fresh produce and a moderate amount of dietary fats.
The Mediterranean diet is full of oily fish, whole grains, extra virgin olive oil, eggs, meats and a variety of fruits and vegetables. This diet is approximately 35-40% fat, mostly for monounsaturated sources.
In a daily food plan, it would look like:
- 1,500 calories: about 58–67 grams of fat per day
- 2,000 calories: about 78–89 grams of fat per day
- 2,500 calories: about 97–111 grams of fat per day
Final note on fat consumption
Dietary fats make up just a small portion of any overall food philosophy. It’s important to take in consideration your lifestyle, your health conditions, and your health and fitness goals before making any drastic switches in your diet.
For a complete guide to meal planning that balances intake of carbohydrates, proteins and dietary fats for athletes, sports and active people, get a copy of my e-book “Fuelling For Fitness”.
Or start with my Free Guide To Carbohydrate & Protein, download the free e-guide here.