Energy Balance

Getting the Equation to Work

The Hard Question

• How much should I eat each day?– What you are doing– Positive/negative or equal energy balance– Need to calculate BMR

Nutrition AppliedPT571001; SP572001; SM569001

Each Person is an Individual

• Largest energy requirements for those who are:– Young– Growing– Large– Muscular– Have long high intensity training sessions

Energy Balance

• Total Daily Energy Intake: (TDEI)– refers to the energy obtained from the diet in a day

period

• Total Daily Energy Expenditure: (TDEE)– refers to all the energy used to power the body

through a day period

• Energy Balance when:TDEI = TDEE

→ amount of energy put into body equals amount of energy spent over the day.

Energy Balance and Body Weight

• If TDEI = TDEE→ body weight (BW) remains stable

• If TDEI > TDEE→ POSITIVE energy balance→body stores extra energy ( BW)

• If TDEI < TDEE→ NEGATIVE energy balance→body uses stored energy to make up

difference ( BW)

Changing energy balance

affects body weight

How Do We Measure Energy Expenditure?

• Indirect Calorimetry– Hard to do in the field

– Measures RER by O2/CO2 ratios

– Reliant on knowing diet and exercise

• Doubly-labelled Water– Accurate but very expensive

• Prediction Equations

Food Energy

• The macronutrients in food provide energy to power body functions.

• Food energy measured in kilojoules (kJ) or kilocalories (kcal or Cal): 1Cal = 4.2kJ

• What you eat is important because:– Different energy kJ/g of each nutrient:

CHO = 16kJ/g Protein = 17kJ/gFat = 37kJ/g Alcohol = 29kJ/g

– Nutrients used differently in the body

Food Energy

1. Alcoholin = Alcoholoxidation

2. Carbohydratein = Carbohydrateoxidation

3. Fatin = Fatoxidation

4. Proteinin = Proteinoxidation

When any of the nutrients in are greater than the oxidation then have food energy stored.

Total Daily Energy Expenditure

TEF

Physical Activity

Basal Metabolic

Rate

• How do we change our TDEE?– BMR– Physical Activity– Thermic Effect of Food

What is TDEE

• The energy used to power the body through 24 hours

• TDEE is made up to 3 parts:1. Basal Metabolic Rate (BMR)

– Energy required for basic body functions– 50-60% TDEE

2. Physical Activity– Includes energy cost of purposeful activities of daily living

and/or planned exercise– 20-40% TDEE

3. Thermic Effect of Food (TEF)– Energy required to process food in the body– <10% TDEE

Basal Metabolic Rate

• Basal metabolic rate influenced by:– Body Size: BMR with body mass– Body Composition: adipose (fat) tissue has lower

energy demand than muscle→ BMR with muscle; with fat.

– Age: BMR with age– Gender: BMR women cf men ( total mass, women

higher fat to muscle ratio)– Genetic component– Nutritional status: adaptive changes to modified

energy intake

Physical Activity

• Most variable component of energy expenditure.• Physical activity energy demand influenced by:

– Type ( with weight bearing/loading)– Intensity ( with intensity)– Duration ( with duration)– Size of Individual ( with size)– Rest between movements ( with rest)– Skill of movement (muscle efficiency) ( with skill)

Factors Affecting TEF

• Genetically determined??

• Diet composition: TEF in response to protein cf fat and CHO

• Very small contributor to total daily energy expenditure