Macronutrients: Fats (AQA GCSE Food Preparation & Nutrition)

Revision Note

Emma Archbold

Written by: Emma Archbold

Reviewed by: Lára Marie McIvor

Macronutrients: fats

  • Fats can be present in food in the form of solid fats and liquid oils

  • Fats have a range of functions in the body, such as:

    • a concentrated energy store

    • production of cell membranes

    • insulating the body to reduce heat loss

    • protecting internal organs against impact damage

    • allowing the absorption of fat soluble vitamins, e.g. A and D

Sources of fats

  • Sources of animal fats include:

    • meat, e.g. bacon and pork belly contain visible fat

    • dairy, e.g. butter and cheese

    • fish

    • eggs

  • Sources of plant fats include:

    • plant oils, e.g. olive oil and sunflower oil

    • avocados

    • olives

    • nuts and seeds

Illustration of foods containing fats including avocado, spinach, beans, salmon, olive oil, eggs, broccoli, and pumpkin seeds arranged on a light background.
Fats are present in foods such as meat, eggs and avocado

Fat deficiency and excess

  • Fats are an essential dietary component, but must be consumed in the correct quantities to avoid deficiency or excess

  • Fat deficiency can result in symptoms such as:

    • the body breaking down protein in order to release energy, which can lead to muscle loss and physical weakness

    • an inability to absorb fat-soluble vitamins, such as A, D, and E, resulting in vitamin deficiencies

    • omega-3 deficiency increases the risk of heart disease

    • increased heat loss

  • An excess of dietary fat can also have negative consequences, such as:

    • weight gain and obesity

      • Obesity increases the risk of other associated conditions, such as type 2 diabetes

    • an increased risk of cardiovascular disease, e.g. high blood pressure, coronary heart disease and stroke

Dietary reference values for fats

  • The dietary reference values for fats state that they should not supply more than 35 % of the energy we get from our food

    • The rest should come from other sources like carbohydrates

  • The average adult should consume around 70 g of fat per day

    • No more than 20 g of this should come from saturated fat (see below)

Saturated and unsaturated fats

  • Fat molecules in food are made up of three fatty acid chains and a single molecule of glycerol

Fat structure diagram

Diagram depicting the structure of a fat molecule with glycerol bonded to three fatty acid chains, labelled accordingly, linked by lines and arrows.
The fat molecules in foods contain fatty acids and glycerol
  • The structure of the fatty acid chains affects the properties of fats

    • Fatty acid chains are hydrocarbons, made up of carbon atoms joined together with hydrogen atoms

  • Fatty acid chains can either be saturated or unsaturated:

    • Saturated fatty acids have only single bonds between carbon atoms; they are 'full up', or saturated, with hydrogen atoms

      • Saturated fats are more likely to be solid at room temperature, e.g. in:

        • meat

        • butter

        • lard

        • coconut oil

    • Unsaturated fatty acids contain at least one double bond between carbon atoms; they are not saturated with hydrogen atoms

      • These fats are more likely to be liquid at room temperature, e.g. in:

        • plant oils, e.g. olive oil, rapeseed oil, sunflower oil

        • oily fish, e.g. salmon

      • Monounsaturated fatty acids contain a single double bond, e.g. avocado and peanut oil

      • Polyunsaturated fatty acids contain more than one double bond, e.g. soybeans and sunflower oil

  • Saturated fats are associated with increased blood cholesterol and are thought to increase the risk of heart disease

  • Increasing the ratio of unsaturated fats to saturated fats in the diet is thought to reduce the risk of heart disease

    • Unsaturated fats are sometimes referred to as 'good fats' for this reason

Examiner Tips and Tricks

Oily fish, such as salmon and tuna, are a much better source of fats than non-oily ones, like cod and haddock, so if you're asked to design a recipe high in unsaturated fats make sure to list some oily examples.

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Emma Archbold

Author: Emma Archbold

Expertise: Biology

Prior to working at SME, Emma was a Biology teacher for 5 years. During those years she taught three different GCSE exam boards and two A-Level exam boards, gaining a wide range of teaching expertise in the subject. Emma particularly enjoys learning about ecology and conservation. Emma is passionate about making her students achieve the highest possible grades in their exams by creating amazing revision resources!

Lára Marie McIvor

Author: Lára Marie McIvor

Expertise: Biology Lead

Lára graduated from Oxford University in Biological Sciences and has now been a science tutor working in the UK for several years. Lára has a particular interest in the area of infectious disease and epidemiology, and enjoys creating original educational materials that develop confidence and facilitate learning.