Measuring Energy Expenditure

Resting metabolic rate

uses 60-75% of TDEE, is the energy costs of processes that are essential for daily life

Diet-induced thermogenesis (DIT)

10% of TDD, energy costs of digesting, absorbing, and storing food.

Activity energy expenditure

15-30% of TDEE, most variable, includes non-exercise activity energy expenditure and purposeful exercise energy expenditure.

Optimal diet

diet that supplies the required nutrients in adequate amounts without excess intake for tissue maintenance, tissue repair, and tissue growth.

Recommended dietary allowance (RDA)

average daily dietary nutrient intake that is sufficient enough to meet the nutrient requirements of 98% of healthy people.

Estimated energy requirement (EER)

average daily dietary energy intake predicted to maintain energy balance in a healthy adult of a defined age, gender, weight, height, and level of physical activity that is consistent with good health.

Calorimetry

the measurement of heat transfer directly or indirectly

Direct calorimetry

measuring heat production by changes in water and air temperature.

Indirect calorimetry

measure O₂ consumption and CO₂ production, more practical

Heat of combustion

heat liberated by oxidizing a specific food, represents the food’s total energy value.

Open circuit spirometry

measuring VO₂ consumption and VCO₂ production by having subject inhale ambient air then exhale all air into instrument that will compare the inhaled vs exhaled air contents, provides an indirect but accurate estimate of energy expenditure.

Doubly labeled water

estimation of total daily energy expenditure in free living conditions, uses hydrogen and oxygen in water to then collect and measure amount of CO₂ is in urine.

Obligatory thermogenesis

energy required to digest, absorb, and store macronutrients.

Facultative thermogenesis

activation of the sensory nervous system and stimulating effect on metabolism.

Basal metabolic rate

the minimum level of energy required to sustain vital functions in the waking state, reflects the body’s total heat production.

Resting metabolic rate

Energy required to maintain normal regulatory balance and body functions at rest, AKA resting energy expenditure. Influenced by surface area, weight, hormones, age, physical activity, muscle mass, and body temperature.

Respiratory quotient (RQ)

indicate fuel utilization at rest and during steady-rate exercise, reflective of O₂ consumption and CO₂ production at a cellular level.

Respiratory exchange ratio (RER)

reflects O₂ consumption and CO₂ production when factors other than macronutrient combustion contribute to gas exchange, calculated during non-steady rate and exhaustive exercise.

RER > 1.0

indicates excess CO₂ production in relation to O₂ uptake, due to buffering during intense exercise that uses sodium bicarbonate to buffer lactic acid.

RER < 0.7

following exercise as CO₂ is retained to replenish the sodium bicarbonate buffer system.

Steady state oxygen consumption

rate of oxygen uptake/consumption by muscles, proportional to the rate of energy ise, rate of ATP use, and rate of caloric expenditure.

Maximal oxygen consumption

oxygen consumption plateau with increasing exercise intensity, maximal amount of oxygen an individual can consume per minute during exercise. Used as an indicator of maximal endurance/aerobic power and capacity. Influenced by genetics (40-50%) and training (can increase 20-40% on top of genetics).

Intensity

how hard you feel the activity is, can be based on % of VO2 max or on Borg scale.

Duration

how long you perform an activity, usually at low intensity daily.

Metabolic equivalent (MET)

Multiples of RMR, 1 MET = the resting oxygen consumption.

Brief, all out exercise

8-10 seconds, high intensity (>95% VO2 max)

Brief, high-intensity exercise

10-30 seconds, high intensity (>91% VO2max)

Middle distance, high intensity exercise

3o seconds- 3 minutes, high intensity (75-90% VO2 max), ex: 400-800m sprint

Prolonged, moderate-high intensity exercise

3-40 minutes, 46-90% VO2 max, ex: 1500-3000m run

Prolonged, low-moderate intensity exercise

>40-minute duration, 37-63% VO2max, ex: marathon

Steady-rate exercise

performing same intensity exercise for the duration of the activity, usually light-moderate intensity.

Non-steady-rate/graded exercise

performing varying intensity of exercise for the duration of the activity, usually moderate to high intensities with rest between or can be slow progression from light to high intensity with defined intervals.