fat

Key points

• Fat provides energy; 1 gram provides 37 kJ (9 kcal). Foods that contain a lot of fat provide a lot of energy.
• Fat is made up of different types of fatty acids. A high intake of saturates can have an adverse effect of health.
• Fat provides essential fatty acids. It is a carrier of fat-soluble vitamins and is necessary for their absorption.
• Fat is needed for health but only in small amounts. No more than about one third of our energy intake should come from fat.

Fat in the diet
The National Diet and Nutrition Survey showed that in 2000/2001, the average daily intake of fat was 87g and 62g for men and women respectively (providing around 36% and 35% of the food energy in the diet, i.e. exclusive of alcohol intake). This indicates that fat now contributes a significantly lower proportion of energy in the UK diet than when the previous survey was carried out in 1986/87 and that on average women are meeting the recommended target for dietary fat of 35% of food energy (see below). However the survey also showed that saturated fatty acids (SFA) provide 13% of food energy for both men and women, which still exceeds the recommended 11

Essential fatty acids
The body can make all the fatty acids it needs except for two, known as alpha linolenic acid and linoleic acid fatty acids. These are called the Essential Fatty Acids (EFAs) and must be supplied in the diet, particularly from oily fish and fish oil supplements. They are also present in the meat or eggs of animals fed omega 3 fatty acid-enriched diets, i.e. foods produced in this way could be considered alternative sources to oily fish, although the amounts of the so called ‘long chain’ omega 3 fatty acids present are typically less than in oily fish.

Saturated and unsaturated fatty acids
The nature of the fat depends on the types of fatty acids which make up the triglycerides. All fats contain both saturated and unsaturated fatty acids but are sometimes described as ‘saturated’ or ‘unsaturated’ according to the proportions of fatty acids present. For example, butter is often described as a ‘saturated fat’ because it has more saturated fatty acids than unsaturated fatty acids, while most vegetable oils are described as ‘unsaturated fats’ as they have more mono- and polyunsaturated fatty acids than saturated.

As a rough guide, saturates are solid at room temperature and tend to be derived from animal sources. Most unsaturates are liquid at room temperature and are usually vegetable fats.

Further information
Department of Health (1994) Report on Health and Social Subjects No. 46. Nutritional Aspects of
Department of Health (1998) Report on Health and Social Subjects 48. Nutritional Aspects of the Development of Cancer. Report of the Working Group on Diet and Cancer of the Committee on Medical Aspects of Food and Nutrition Policy. Stationary Office, London.
Henderson L, Gregory J, Irving K et al (2003) The National Diet and Nutrition Survey: Adults Aged 19-64 years, Volume 2: Energy, Protein, Carbohydrate, Fat and Alcohol Intake. London, HMSO.

© British Nutrition Foundation