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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