Energy Needs (AQA GCSE Food Preparation & Nutrition)

Understanding energy needs

• To determine energy requirements it is important to consider:

  • Basal metabolic rate (BMR)

  • Physical activity level (PAL)

Basal metabolic rate

• This is the metabolic rate when the body is at rest

  • The smallest amount of energy required to stay alive to breathe and for the heart to beat during one day

  • Around 75 % of our energy intake each day is used for BMR

• It is affected by:

  • age

  • physical health

  • biological sex (gender)

  • weight and height

  • physical activity level

Age

• As we age, our bodily functions slow down, and this slows our BMR, particularly due to lower muscle mass

• Older people tend to then store more mass as fat which contributes to a change in their BMR

Physical health

• The more exercise a person does, the greater their muscle mass

• This will increase the BMR

Biological sex (gender)

• Females generally have a lower BMR than males as (due to genetic predisposition) females have a lower muscle mass than males and so this lowers BMR

Weight and height

• A person who has a larger weight and height will have a higher BMR as they require more calories

Physical activity level (PAL)

• PAL is a measure of how active a person is and how much exercise they do

• It is calculated by taking into consideration how many physical activities are carried out in a day and how energetic the exercises are

• A higher PAL denotes that the person is more active

Daily energy requirements

• BMR and PAL can be used together to calculate a daily energy requirement, where (kcal) is kilocalories

• A high BMR and PAL will mean that a person has a higher energy requirement, whereas a low BMR and low PAL will mean a lower energy requirement

• Managing daily energy requirements is important to maintain a healthy body weight and must be balanced

  • Consuming more energy (calories) than required will mean a person gains weight

  • Consuming less energy (calories) than required will mean a person loses weight

• Each nutrient has a recommended percentage of energy intake and portion sizes should consider this: