Energy Needs
Food Preparation & Nutrition: AQA GCSE, topic 2.3.3
Basal Metabolic Rate and Physical Activity Level
Basal metabolic rate (BMR) and physical activity level (PAL) are measures of energy requirement and activeness respectively.
Basal metabolic rate (BMR)
- BMR - the absolute minimum level of energy required to stay alive. It covers basic life processes, like breathing and maintaining a heartbeat.
- These processes can take up almost 75% of our daily energy use. The rest is used up by processes like digestion and physical activity.
Factors affecting BMR
- Age - our muscle mass reduces with age. This causes BMR to decrease.
- Sex - as women are generally smaller and have less muscle mass than men, they tend to have lower BMRs than men.
- Exercise/physical activity - the more a person exercises, the more muscle they'll build up. This will raise their BMR.
- Height and weight - the larger or heavier a person's body, the more calories they need and the higher their BMR.
Physical activity level (PAL)
- PAL - a measure of how much exercise someone does or how active they are.
- The more active a person, the higher their PAL will be.
Daily energy requirement equation
- Daily energy requirement (kcal) = BMR × PAL
Balancing energy intake
- To stay at a healthy weight, a person must balance their energy intake.
- A person will gain weight if they consume more energy than they use.
- A person will lose weight if they consume less energy than they use.
Recommended Percentage Intakes
Our main energy sources are proteins, carbohydrates and fats. Government guidelines recommend that we eat them in certain proportions:
Carbohydrates - 50%
- We should get most of them from starchy foods and naturally-occurring sugars (from milk (lactose) and fruit (fructose)).
- A maximum of 5% should come from added sugars.
Fat - 35%
- 35% is recommended as a maximum. Consuming less is fine.
- We should try and consume as little saturated fat as we can.
Protein - 15%
- We should try to eat a mix of proteins (animal and plant based).
Test yourself on Energy Needs
What is the equation for daily energy requirement?
What does BMR stand for?
Balancing Energy Sources
What are our main energy sources?
Which energy source should make up 35% of our diet?