Chapter 14 Energy Balance and Body Composition

Chapter 14: Energy Balance and Body Composition

Introduction

  • Observation of health discussions in media about weight management (loss or gain).

  • Importance of energy balance: balancing intake (food & drinks) with kilocalories burned.

  • Factors affecting weight include genetics, environment, and others.

What Is Energy Balance and Why Is It Important?

LO 14.1 Define Key Terms

  • Energy Balance: Relationship between energy intake and expended energy.

  • Positive Energy Balance: When energy intake > energy expenditure, leading to potential weight gain from muscle mass or adipose tissue accumulation.

  • Negative Energy Balance: When energy intake < energy expenditure, resulting in weight loss mainly from fat loss.

Energy Balance Overview

  • Energy in equals energy out results in stable body weight.

  • Positive energy balance is crucial during growth phases (pregnancy, childhood, adolescence) and recovery from illness.

  • Every 3,500 excess kilocalories lead to approximately one pound of weight gain.

  • Long-term, a modest, chronic positive energy balance leads to weight gain.

Energy Imbalance and Weight Management

  • A sustained positive energy balance can lead to significant weight gain, primarily as fat in adipose tissue.

  • Negative energy balance leads primarily to fat loss but can also cause loss of muscle mass, glycogen, and water weight.

Energy Intake

  • Energy is derived from carbohydrates, proteins, fats, and alcohol.

  • Bomb Calorimeter: Measures heat produced during food combustion for kilocalorie assessment.

    • One kilocalorie raises 1 kg of water by 1°C.

  • Physiological Fuel Values: Corrected energy values, e.g., protein yields approximately 4.27 kilocalories per gram after digestion adjustments.

Energy Expenditure

Body Processes and Activity

  • Body processes (digestion, respiration) and physical activity contribute to energy expenditure.

  • Individual differences in energy expenditure depend on daily activities.

  • Average daily energy expenditure (TDEE) is critical for maintaining weight or achieving weight goals.

Components of Total Daily Energy Expenditure (TDEE)

  1. Basal Metabolism (BMR): Energy for vital functions when at rest (50-70% of TDEE).

    • Determined by lean body mass (muscle, bone), age, gender, body size, genes, ethnicity, and some hormonal and environmental factors.

  2. Thermic Effect of Food (TEF): Energy used to digest and process food, about 10% of caloric intake.

    • Varies by nutrient type (e.g., proteins 20-30%, carbohydrates 5-10%, fats 0-3%).

  3. Thermic Effect of Exercise (TEE): Energy required for physical activities, dependent on the type, duration, and individual weight.

    • Nonexercise activity thermogenesis (NEAT) also contributes.

LO 14.1: The Take-Home Message

  • Energy balance relates to intake and expenditure. Positive balance results in weight gain, negative balance results in weight loss.

  • Energy intake from foods and physical activity accounts for energy expenditure.

Total Daily Energy Expenditure Calculation

LO 14.2 Discuss TDEE Calculation Factors

  • Factors include BMR, TEF, and TEE.

  • Basal Metabolic Rate (BMR) calculation methodologies:

    • Direct Calorimetry: Measures heat generated using metabolic chambers but is impractical for regular use.

    • Indirect Calorimetry: Measures oxygen consumption and carbon dioxide output (more common).

Simple Calculation Methods

  • Estimated Energy Requirement (EER) considers gender, age, height, weight, activity level. Activity levels have numerical values ranging from sedentary (1.00) to very active (1.45-1.48).

LO 14.2: The Take-Home Message

  • TDEE is divided into BMR, TEF, adaptive thermogenesis, and TEE.

Body Composition and Assessment

LO 14.4 Define Body Composition

  • Body composition refers to the ratio of fat tissue to lean body mass.

  • Types of body fat include essential fat (vital for physiological functions) and stored fat in adipocytes.

    • Women generally have higher essential fat amounts than men.

Health Implications of Body Fat

  • Carrying excessive body fat can impair health and is linked to various diseases.

  • Central (android) obesity (fat stored around the waist) increases the risk of chronic diseases; Gynoid obesity (fat stored around hips) is less risky.

Assessment Methods

  1. Hydrostatic Weighing: Measures body density via water displacement, accurate with a margin of error of 2-3%.

  2. Air Displacement (BodPod): Similar principles, faster but limited by availability.

  3. Dual-Energy X-ray Absorptiometry (DEXA): The most accurate with a 1-4% margin of error, assesses fat, lean mass, and bone mass.

  4. Bioelectrical Impedance Analysis (BIA): Measures resistance to electrical flow; accuracy can vary based on hydration.

  5. Skinfold Measurements: Use calipers to measure skinfold thickness for body fat estimation, reliant on trained technicians.

Waist Circumference

  • A waist measurement above 35 inches (women) or above 40 inches (men) increases health risks.

LO 14.4: The Take-Home Message

  • Key distinctions in body composition and assessments reflect health risks related to fat distribution.

Estimating Healthy Body Weight

LO 14.5 Methods of Estimation

  • Body weight is measured in pounds (lb) or kilograms (kg), whereas composition indicates percentage of body fat to lean mass.

  • Body Mass Index (BMI):

    • Calculated as:

    • BMI = Weight (kg) / height² (m²)

    • BMI = (Weight (lb) x 703) / height² (inches)

  • BMI Categories:

    • Underweight: BMI < 18.5

    • Healthy: BMI 18.5-24.9

    • Overweight: BMI 25-29.9

    • Obese: BMI ≥ 30, with severe obesity at BMI ≥ 40.

Health Risks Associated with BMI

  • Elevated BMI correlates with increased health risks and mortality.

  • BMI’s limitations include not distinguishing between fat and muscle or fat distribution specifics.

Combining Measurements for Better Estimates

  • Combining BMI with waist circumference provides better health risk assessments.

LO 14.5: The Take-Home Message

  • BMI and height–weight tables are useful but limited; understanding body composition is crucial for health risk evaluation.

Disordered Eating

LO 14.6 Diagnosis Criteria for Eating Disorders

  • Definition of disordered eating as abnormal and potentially harmful patterns.

  • Clinical eating disorders include anorexia nervosa, bulimia nervosa, and binge eating disorder.

Shared Traits of Eating Disorders

  • Obsession with food and distorted body image common across disorders.

  • Psychological aspects include low self-esteem, shame, and control issues.

  • Societal pressures contribute significantly to the rise of eating disorders.

Diagnostic Criteria Table (14.8): Eating Disorders Criteria

  1. Anorexia Nervosa: Energy intake restriction, intense fear of weight gain, body image distortion.

  2. Bulimia Nervosa: Recurrent binge episodes followed by inappropriate compensatory behaviors.

  3. Binge Eating Disorder: Binge eating episodes without purging, marked distress afterward.

Other Specified Feeding and Eating Disorders (OSFED)

  • Includes a variety of abnormal eating patterns not fitting classic diagnostic criteria yet require treatment.

Effective Treatments for Eating Disorders

  • Multidisciplinary approaches integrating psychological, medical, and nutritional therapies show the best outcomes for recovery.

  • Early intervention is key for effective treatment and possible full recovery.

LO 14.6: The Take-Home Message

  • Understanding disordered eating behaviors and having access to effective treatment options are essential for supporting individuals struggling with these issues.