Lecture 22 Energy Expenditure Methods to assess EE

Lecture Overview

• Title: FNH 350 – Fundamentals of Nutrition

• Topic: Energy Metabolism

• Focus: Components of Energy Expenditure

Learning Objectives

• Components of Energy Expenditure:

  • Describe components affecting energy expenditure.

  • Define Basal Metabolic Rate (BMR) and influencing factors.

  • Identify organs contributing to basal metabolism.

  • Differentiate between Basal Metabolic Rate and Resting Metabolic Rate (RMR).

  • Explain the Thermic Effect of Food (TEF).

  • Significant roles of thermoregulation and physical activity.

• Energy Intake and Expenditure:

  • Evaluate energy loss and methods for energy expenditure assessment.

  • Understand direct calorimetry, RQ, and the doubly-labeled water method.

  • Factors influencing total estimated energy requirements.

Energy Components

• Energy Intake:

  • Carbohydrates, Lipids, Proteins, Alcohol

• Energy Expenditure:

  • BMR: 50-70% of total energy expenditure

  • Physical Activity: 20-40%

  • Thermic Effect of Food: involves digestion and absorption, contributing 5-30% increase in energy expenditure above BMR.

Basal Metabolic Rate (BMR)

• Definition: Energy required to sustain basic life processes including respiration, heartbeat, renal function, blood circulation, and maintaining an awake state.

• Measurement:

  • Assessments include measuring O2 consumption and CO2 production under controlled conditions: fasting (12-14 hours), lying down, awake, and relaxed.

• Organ Contributions:

  • Major contributors: liver, lungs, heart, brain, kidneys (60-80% of BMR)

  • Muscle contributes < 25%

Resting Metabolic Rate (RMR)

• Definition: RMR is the energy expenditure in a resting, post-absorptive state while awake but after fasting for 4-5 hours.

• Difference from BMR: RMR is approximately 10% higher due to its conditions of being tested without food intake or recent exercise.

Thermic Effect of Food (TEF)

• Overview: Increased energy expenditure associated with processing ingested food, accounting for approximately 10% of total energy expenditure.

• Protein: Most significant effect (20-30% increase)

• Carbohydrates: Intermediate effect (5-10%)

• Fats: Smallest effect (0-5%)

Thermoregulation

• Function: Adjusts metabolism to maintain body temperature. Normal body temperature is approximately 37°C.

• Environmental Influence:

  • Cold conditions increase metabolic rate due to shivering.

  • Hot conditions increase metabolic rate through sweat gland activity.

• Medical Emergencies:

  • Hypothermia (<35°C) can result in slowed metabolism, fatigue, and disorientation.

  • Hyperthermia (>37.5°C) indicates failed thermoregulation and poses health risks.

Energy Expenditure of Physical Activity

• Characteristics:

  • Accounts for the most variability in energy expenditure (20-40%).

  • Influenced by intensity, duration, and frequency of activity.

  • Post-activity energy expenditure may remain elevated.

Assessment Methods

• Energy Expenditure Measurement:

  1. Direct Calorimetry: Measures heat dissipation from the body.

     • Advantages: Direct measurement of energy loss.

     • Limitations: Costly, labor-intensive, potentially uncomfortable.

  2. Indirect Calorimetry: Measures O2 consumption and CO2 production; relies on estimating energy substrates used.

  3. Doubly Labeled Water Method: Involves stable isotopes to measure energy expenditure and metabolic rate.

Estimated Energy Requirements (EER)

• EER Definition: Dietary energy intake needed to maintain energy balance in healthy adults considering age, sex, weight, height, and physical activity.

• Factors Affecting EER: Changes with age, metabolic needs can vary based on physiological states (e.g., pregnancy, activity level).

Final Notes

• Review Sessions: Focus on main concepts for upcoming final exams in December.

• Classroom Engagement: Clicker questions used to assess understanding and promote active learning.