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Macronutrients Explained: Fat

Fat is an essential macronutrient made up of fatty acids.


1g fat = 9kcals.


Fats are consumed in the diet in the form of animal fats, sterols, oils and phospholipids.


Fats are broken down in the body into fatty acids during digestion. These can then go on to form more complex lipid molecules such as triglycerides, phospholipids and steroids.

Some fatty acids are essential

  • Alpha-linolenic acid (ALA) (an omega-3 fatty acid)

  • Linoleic acid (LA) (an omega-6 fatty acid)

So must be obtained through the diet. Others are nonessential and can be synthesised endogenously in the body from the above fatty acids.


At some stages in life some fatty acids become essential, and so are 'conditionally essential' . For example the non-essential fatty acid docosahexaenoic acid (DHA) is essential during childhood for brain development.


Fatty acids can be categorised into three types based on their molecular structure:

  • Saturated (SFA)

  • Polyunsaturated (PUFA)

  • Monounsaturated (MUFA)

Saturated fats tend to be found in larger quantities in animal products and are solid at room temperate, for example in butter.


Whereas unsaturated fats tend to be found in larger quantities in plant sources and are liquid at room temperature, for example in olive oil.

Below are lists of examples of foods where the types of dietary fats can be found.


Trans fatty acids are primarily man made sources of fat that are also strongly associated with negative health outcomes. These include hydrogenated vegetable oils which are found in many processed foods like spreads, snack foods and pastries to extend their shelf life.


FUNCTIONS OF FAT


  • Needed for cell structure, signalling, intracellular messaging & more

  • Needed for absorption of fat soluble vitamins

  • Needed for sex hormone production and function (testosterone, progesterone, oestrogen)

  • Provides us with a large, slow energy source

  • Needed for the production of recovery hormones (Gropper, 2017)


Reducing saturated fat intake has been shown to lower circulating levels of blood cholesterol, specifically the low density lipoproteins (LDL) that bind cholesterol for transportation around the body.


Higher serum LDL-C levels and longer exposure to this increases risk of atherosclerotic cardiovascular disease (ASCVD) (Boren, 2020).


Due to this causal nature it is recommended that the average contribution of saturated fatty acids to (total) dietary energy be reduced to no more than 10% per day and that SFA be substituted with unsaturated fats, specifically PUFAs for further reductions in risk (SACN, 2019)