Energy and Metabolism Quiz

Energy and Metabolism

• Metabolism refers to the chemical reactions in the body that release energy from food.
• A calorie is a unit of heat energy.
• Kilocalories (kcal) are used to express the energy in food.
• One gram of carbohydrates, protein, and fat contain 4, 4, and 9 kcal respectively.
• The basal metabolic rate (BMR) is the amount of energy required to maintain essential bodily functions at rest.

Energy Balance

• Energy balance is the relationship between energy intake and energy expenditure.
• Factors affecting energy expenditure include physical activity, BMR, and specific dynamic action (SDA).
• SDA is the extra energy used by the body to process food.

Factors Affecting BMR

• Body surface area: Taller people have higher BMRs.
• Sex: Males have higher BMRs due to a greater lean body mass.
• Body temperature: Fever increases BMR
• Hormones: Thyroid hormones stimulate metabolism leading to higher BMR in hyperthyroidism and lower in hypothyroidism.
• Age: BMR declines with age.
• Diet: Starvation or calorie restriction significantly reduces BMR.
• Pregnancy/breastfeeding: Increase metabolic rate.
• Environment: Cold climates result in higher BMR compared to warm climates.
• Rapid growth & development: Infancy, growth spurts, recovery from illness or injury increase BMR
• Disease states: BMR is higher in certain conditions like cardiac failure, leukemia, and hypertension.
• Weight: Higher weight leads to higher BMR.
• Exercise: Regular exercise builds lean tissue which raises BMR and results in higher calorie expenditure.

Body Weight and Body Mass Standards

• Ideal body weight refers to the optimal weight for good health.
• Body Mass Index (BMI) is a more reliable indicator of healthy weight, based on height and weight.
• BMI is calculated by dividing weight in kilograms by the square of height in meters.
• BMI is a general indicator and may not be accurate for individuals with fluid retention, athletes, or the elderly.

Caloric Needs

• Total Daily Energy Expenditure (TDEE) is the total number of calories burned by the body in 24 hours.
• Calculating TDEE involves accounting for BMR, physical activity, and SDA.
• Example calculations for individuals with varying levels of work demonstrate the energy requirements for different daily activities.
• The caloric requirements for different work types are:
  • Light work: 2100-2600 kcal/day
  • Moderate work: 2500-3000 kcal/day
  • Heavy work: 3000-3500 kcal/day
  • Very heavy work: 3500-4000 kcal/day