Energy and Energy Balance - Week 3

Macronutrients vs. Micronutrients

Macronutrients provide energy; micronutrients (vitamins and minerals) do not.

SI Unit for Energy

Kilojoules (kJ); 1 kilocalorie equals 4.2 kilojoules.

Bomb Calorimeter

Device that directly measures energy in food by burning it.

Atwater Factors

Population averages for metabolizable energy in macronutrients and alcohol.

Components of Energy Expenditure

Resting metabolism, physical activity, and thermic effect of food.

Basal Metabolic Rate (BMR)

Energy expended in a fasted, rested state.

Thermic Effect of Food (TEF)

Energy increase during digestion, absorption, and metabolism of food.

TEF Macronutrient Hierarchy

Protein produces a greater thermic effect than carbohydrate and fat.

Physical Activity Energy Expenditure

Most variable component; includes active exercise, incidental activity, and fidgeting.

Direct Calorimetry

Gold standard method measuring heat produced by the body.

Doubly Labelled Water Method

Free-living energy expenditure method using 2H and 18O isotopes.

Indirect Calorimetry

Measures energy expenditure via oxygen consumption and carbon dioxide production.

The Factorial Method

Estimates energy requirements by multiplying BMR by Physical Activity Level.

Schofield Equation

Predictive equation using gender, age, and weight to estimate BMR.

Physical Activity Level (PAL)

Multiples of BMR used to adjust for physical activity.

Doubly Labelled Water Method - Strengths

Accurate for free-living conditions and measures total daily energy expenditure over weeks.

Doubly Labelled Water Method - Limitations

Expensive and requires sophisticated mass spectrometry analysis.