Energy

Energy in the Body

Energy is essential for all body functions and tasks, such as:

• Digesting food, breathing, thinking, walking, and working.
• Food is broken down in the body through a process called oxidation, where oxygen is used to create heat and energy.

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Measuring Energy

• Energy from food is measured in:
  • Kilocalories (kcal).
  • Kilojoules (kJ).
• Conversion Tip:
  • To convert kilocalories to kilojoules, multiply by 4.18.
  • Example: 100 kcal = 418 kJ.

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Energy Balance

• Basal Metabolic Rate (BMR):
  • The basic amount of energy needed to keep the body functioning at rest.
• Energy Balance:
  • Achieved when energy input (from food) equals energy output (BMR + physical activity).
  • Maintaining energy balance helps keep a healthy body weight.

Energy Output Examples (kcal per hour):

Activity	Energy Used (kcal/hour)
Sleeping	70
Sitting	85
Writing	115
Housework	250
Swimming	500
Running/football	900

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Factors Influencing Energy Requirements

1. Gender:

• Males usually require more energy than females due to higher muscle mass.

2. Climate:

• Colder climates increase energy needs to maintain body heat.

3. Activity Levels:

• Active people need more energy than those with a sedentary lifestyle.

4. Pregnancy and Breastfeeding:

• Increased energy is required to support the baby and milk production.

5. Age:

• Growing children and teenagers need more energy than adults.

6. Size:

• Smaller individuals generally need less energy than larger ones.

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Daily Energy Requirements by Life Stage

Life Stage	Energy Needs (kcal/day)
Baby	800
Toddler	1,300
Child	1,400–2,000
Female Adolescent (Sedentary)	1,800
Female Adolescent (Active)	2,000
Male Adolescent (Sedentary)	2,200
Male Adolescent (Active)	2,400–2,800
Pregnant Female	2,400
Breastfeeding Female	2,700 (Lactation)
Female Adult (Sedentary)	1,800
Male Adult (Sedentary)	2,000
Older Female (Sedentary)	1,600
Older Male (Sedentary)	2,000