Nutrition Energy Quiz

Energy Fundamentals

• Energy is defined as the capacity to perform work.
• Food yields energy through combustion, producing CO2, H2O, and energy.
• Carbohydrates and fats primarily release energy, while proteins produce energy and urea upon combustion.

Energy Yielding Nutrients

• Energy yielding nutrients include carbohydrates, fats, and proteins.
• These nutrients are essential for metabolic processes and physical activity.

Units of Energy

• Energy content in food is expressed in kilocalories (kcal).
• 1 kilocalorie raises the temperature of 1 kg of water by 1°C.
• Joules (J) is now favored as the energy unit in nutrition; 1 kcal is equivalent to 4.184 kJ.

Measuring Energy Value

• Direct calorimetry uses a bomb calorimeter to measure heat from food combustion, providing an accurate energy estimate.
• Indirect calorimetry estimates energy needs by monitoring oxygen consumption in a closed-circuit system.

Gross Energy Value and Metabolizable Energy

• Heat of combustion (gross energy value) is the total energy from food oxidation.
• Metabolizable energy (ME) accounts for energy losses through waste, calculated as: GE - losses = ME.

Physiological Fuel Value

• Physiological fuel value is the actual energy available to the body from nutrients post-digestion.
• Coefficient of digestibility indicates how much of a nutrient is absorbed: carbohydrates (0.98), fats (0.95), proteins (0.92).
• Atwater Bryant factors quantify usable energy: carbohydrates (4 kcal), fats (9 kcal), proteins (4 kcal).

Components of Energy Expenditure

• Energy expenditure consists of three components: basal metabolic rate (BMR), physical activity, and the thermic effect of food.

Basal Metabolic Rate (BMR)

• BMR represents energy for involuntary body functions, including organ function and maintenance of body temperature.
• Influenced by factors such as body composition, gender, age, body size, sleep, and temperature.

Factors Affecting BMR

• Body Composition: More muscle increases BMR; fat is less metabolic.
• Gender: Men generally have a higher BMR than women.
• Age: BMR peaks in early childhood and declines by about 2% per decade after 21.
• Body Size: Larger surface area correlates with higher metabolism.
• Sleep: BMR decreases during sleep.
• Body Temperature: Elevated temperatures can raise BMR.
• Hormones: Thyroxine from the thyroid gland significantly influences metabolic rate.

Additional Influences on BMR

• Pregnancy: Increased BMR (up to 12%) due to fetal demand.
• Nutrition State: Prolonged calorie deficit reduces BMR by 20-30%.
• Environmental Temperature: Extreme temperatures increase energy expenditure.
• Smoking and Genetics: Smoking can boost BMR; genetic variability affects metabolic rates.
• Psychological State: Anxiety can elevate energy expenditure.
• Pharmacological Agents: Nicotine and caffeine can increase energy expenditure; beta-blockers may decrease it.
• Disease Processes: Certain conditions, like fever or burns, may enhance metabolic rates.

Physical Activity

• Following BMR, physical activity significantly contributes to total energy expenditure.
• Energy expenditure varies based on work intensity, type of activity, and duration.

Conclusion

• Understanding energy components and their influences is crucial for nutritional science and health management.