Energy requirements

Energy Requirements

• Learning Objectives:

  • Energy Expenditure/Balance

  • Measuring energy expenditure

  • Assessing dietary intake

Components of Energy Expenditure

• Total Energy Expenditure (TEE)

• Components:

  • Volitional Exercise Physical Activity

  • Non-Exercise Activity Thermogenesis (NEAT)

  • Thermic Effect of Food (TEF)

  • Basal Metabolic Rate (BMR)

Factors Affecting Basal Metabolic Rate (BMR)

• Key Factors:

  • Fat mass

  • Sex (adjustment after accounting for body composition)

  • Growth rate

  • Age

• Other Influencing Factors:

  • Fever

  • Stress

  • Environmental temperature

  • Thyroxine levels

  • Fasting states

Contributions of Organs/Tissues to BMR (Elia, M. 1992)

• Tissue/Organ BMR (Kcal/kg/day):

  • Heart: 440

  • Kidneys: 440

  • Brain: 240

  • Liver: 200

  • Skeletal muscle: 13

  • Adipose tissue (white): 4.5

• % Contribution to Total BMR based on body weight

Thermic Effect of Food (TEF)

• Characteristics:

  • 8-10% increase in oxygen consumption post-meal

  • Peaks at 1 hour, dissipates 4-5 hours post-meal

  • Magnitude of TEF based on food types:

    • Protein: 15-20%

    • Carbohydrate: 6-8%

    • Fat: 2-3%

  • TEF is affected by weight loss

Physical Activity Thermogenesis (PAT)

• In elite athletes, thermic effect of activity may exceed regular levels

• Non-Exercise Activity Thermogenesis (NEAT) shows high variability among individuals

Methods for Assessing Energy Expenditure

• Methods:

  • Direct calorimetry

  • Indirect calorimetry

  • Doubly-labelled water technique

  • Prediction equations

Doubly-Labelled Water Technique

• Components:

  • Utilizes 2H (deuterium) and 18O for human consumption

  • Monitors CO2 production via rate differentials of 2H and 18O losses

  • Considered the gold standard for measuring energy expenditure over 14 days

  • Expensive method of assessment

Predictive Equations for Energy Requirements

• Based on:

  • Age

  • Height

  • Weight

  • Gender

• Equations determine BMR, Resting Metabolic Rate (RMR), or TEE

• Specific equations tailored for:

  • General public (Institute of Medicine, Harris-Benedict)

  • Athletes (Harris-Benedict, Cunningham)

  • Clinical populations

Energy Balance

• Weight Dynamics:

  • Weight gain: More energy in than out

  • Weight loss: More energy out than in

  • Positive energy balance: Excess consumption

  • Negative energy balance: Caloric deficit

  • Energy sources include:

    • Carbohydrate (glycogen, glucose)

    • Body protein (amino acids)

    • Fat (fatty acids)

Societal Influences on Energy Balance

• Health considerations impacting energy balance:

  • Societal pressures (education, cultural, economical)

  • Psychological and social factors affecting consumption

  • Time constraints and perception of food availability

  • Psychological ambivalence around food choices

Assessing Dietary Intake

• Nutritional Assessments Purpose:

  • Identify nutritional needs

  • Assess macro- and micronutrient intake adequacy

  • Connect dietary habits to health outcomes

  • Basis for dietary interventions

• Methods of Dietary Intake Assessment:

  • Food diary or food intake record

  • Food Frequency Questionnaires

  • 24-hour recall

Detailed Assessment Methods

• 3 Day Food Record:

  • Direct intake recording across 2 weekdays and 1 weekend day

  • Provides accurate macronutrient assessments

  • Uses household food measurements

  • Disadvantages: Risk of under/overestimation, limited detail

• 7 Day Food Record:

  • More accuracy with micronutrients

  • Compliance issues noted

  • Inclusion of photo records recommended

• Food Frequency Questionnaire:

  • General intake assessment method

  • Qualitative approach with series questions

• 24-Hour Recall:

  • Interviewer-led, recalls previous day’s intake

  • Efficient and cost-effective

  • Disadvantages: Potential underreporting and inaccuracy in portion sizes.