Food supplies living organisms with energy and nutrients. A balanced diet must contain:
- Carbohydrates and fats to provide energy
- Protien for growth and repair of tissues- energy if carbs in short supply
Carbs are made up of simple sugars, glucose, and are stored in the liver as glycogen or can be converted into fats. Fats are made up of fatty acids and glycerol and are stored under the skin and around organs. Protiens are made up of amino acids and are not stored.
Other substances that don't provide energy, but are needed to keep healthy:
- Minerals, e.g. iron to make haemoglobin in red blood cells
- Vitamins, e.g. vitamin C to prevent scurvy
- Fibre to prevent constapation and to maintain healthy bowels
- Water to prevent dehydration, and to help remove waste
Might alter diet due to:
- Beliefs about animal welfare, e.g. vegitarians/vegans
- Religious beliefs, e.g. Muslim and Jewish faiths prohibit the eating of pig meat
- Medical issues, and food allergies, e.g. some people are allergic to peanuts
- Age- older people need less food (fewer calories); younger people need more calories as they are more active, and more protien
- Sex- males need more calories due to being largr and having more muscle
- Activity- someone with a physical job, e.g. a builder, will need more calories than an offer worker
- Personal choice
How Much Energy is Needed?
Amount of energy needed depends on age, sex, and activity levels.
To maintain healthy body mass, balance amount energy consumed with amount of energy used up through daily activities.
Calculate Body Mass Index (BMI): BMI=Mass (kg)/Height(m)2
BMI <18.5 is underweight. BMI 18.5-24.9 is ideal weight.
BMI 25-29.9 is overweight. BMI >30 is obese.
If you consume more food than you need you will become pverweight or obese. Obesity is a major health problem in the developed world. It can lead to arthritis, heart disease, type II diabetes and breast cancer.
Protein molecules are long chains of amino acids. Essential amino acids must be taken in by eating foo- they can't be madde in body. Non-essential amino acids can be made.
Protein supplies the nutrients that enable you to grow- important for teenagers to have high-protein diet.
Proteins from animal origin are called first class proteins because they contail all essential amino acids. Plant proteins are second class proteins.
In some parts of the world, food is in short supply so people don't get enough protein in their diet. In children, protein deficiency results in a disease called kwashiorkor which is common in poorer countries due to overpopulation and limited investment in agriculture.
Estimated Average Daily Requirement for protein using this formula: EAR=0.6 x Body Mass (kg). EAR is an estimated daily figure for an average person of a certain body mass- can vary depending on age, pregnacy and lactaion.
Protein is only used as an energy source when carbs or fats are unavailable.
Poor Diets and Eating Disorders
Low self-esteem, poor self-image and a desire for perfection can lead to a poor diet.
Poor diets can be very damaging to the body. The body doesn't get the balance of energy and nutrients to function correctly. The reproductive system may be affected as well as damage to the bones.
Eating disorders such as anorexia nervosa or bulimia nervosa may occur.