Ch 8

Chapter 8: Energy Balance & Body Composition

Overview

  • Energy In and Energy Out are critical concepts in understanding body composition and weight regulation.

Objectives

  1. Energy Balance

    • Explain energy balance and consequences of imbalance.

    • Discuss influences on food intake (physical, emotional, environmental).

    • Identify components of energy expenditure and how they are affected.

    • Compare body weight vs. body composition; detail assessment methods like BMI and waist circumference.

    • Link body weight to chronic diseases (health risks for underweight, overweight, and obesity).

Energy Balance

  • Definition: Body weight remains stable when energy (E) consumed = energy expended.

    • E consumed > E expended → weight increase

    • E consumed < E expended → weight decrease

    • 1 lb. of body weight ~ 3,500 kcalories.

  • Hunger Signals: Hormonal and nervous system communication indicates hunger.

3500 kcalorie Rule Limitations

  • Does not consider metabolic changes during weight loss; often overestimates weight loss potential.

  • Does not factor body composition influence on energy needs; calorie deficits differ significantly between genders and weight categories.

  • Body weight components: Fat, fluid, and lean tissues. Loss of body water (60% of body weight) can drastically affect weight.

Energy Terms

  • Bomb Calorimeter: Measures heat energy during food combustion.

  • Direct Calorimetry vs. Indirect Calorimetry: Measures emitted heat vs. O2 consumed and CO2 expelled.

Energy In: Food Intake

Appetite and Hunger

  • Appetite stimulates eating, controlled by the hypothalamus; responses to sight, smell, and taste.

  • Satiation: Sense of fullness guiding meal cessation.

    • Protein is most satiating; high-fat foods promote fullness; complex carbohydrates more satisfying than simple sugars.

Food Calorie Comparison

  • High-fat peanuts are more calorically dense than popcorn; choosing high-fiber foods may provide more nutrients for fewer calories.

Energy Content Calculation

  • Estimate energy values based on macronutrient composition (carbs, fats, proteins).

Energy Expenditure Components

  1. Basal Metabolic Rate (BMR)

    • Majority of E Expenditure: Accounts for ~2/3 of total energy expenditure.

    • Factors Influencing BMR:

      • Height, growth, body composition, environmental temperature, and hormonal changes can increase or decrease BMR.

  2. Physical Activity

    • Most variable component; affected by duration, frequency, and intensity.

    • Critical for weight management strategies.

  3. Thermic Effect of Food (TEF)

    • Represents ~10% of total energy expenditure, varies with macronutrient type.

      • Protein: 20-30%, Fat: 0-5%, Carbs: 5-10%, Alcohol: 15-20%.

  4. Adaptive Thermogenesis

    • Adjustments to energy expenditure based on environmental adaptations.

Body Weight vs. Body Composition

Healthy Body Weight Definition

  • Body Mass Index (BMI):

    • Calculated as weight (kg) / height (m)²; ranges define categories:

      • Underweight: < 18.5

      • Healthy weight: 18.5 - 24.9

      • Overweight: 25 - 29.9

      • Obese: ≥ 30

  • BMI does not measure body composition directly.

Fat Distribution

  • Central obesity: Excess fat around the trunk increases health risks.

  • Waist circumference indicators: High risk if ≥ 35 in women and ≥ 40 in men.

Methods of Assessing Body Composition

  • Hydrodensitometry: Weight comparison underwater to estimate body fat percentage.

  • Bioelectrical Impedance Analysis (BIA): Resistance to electric current indicates body fat levels.

  • Dual-energy X-ray Absorptiometry (DXA): Precise measurement of body fat compared to lean mass.

Health Risks Associated with Weight

Overweight and Health Risks

  • Associated with diabetes, hypertension, cardiovascular issues, some cancers, and psychological issues.

  • Underweight Health Risks: Nutrient deficiencies, weakened immune function, and potential developmental issues.

Inflammation & Metabolic Syndrome

  • Characteristics include hypertension, high blood glucose, and increased waist circumference

  • Note: Inflammation is an immune response to injuries.

Eating Disorders

Definitions and Characteristics

  • Anorexia Nervosa: Distorted body image, self-control issues, dangerous physical and psychological effects.

  • Bulimia Nervosa: Binge-purge cycles, significant health impacts such as dental and emotional issues.

  • Binge Eating Disorder: Involves periods of excessive eating without purging; high potential for treatment.

Tips for Combating Eating Disorders

  • Avoid restrictive eating; focus on frequent balanced meals.

  • Develop supportive groups and set healthy, realistic goals for weight management.”

  • Emphasize nutrition quality for performance rather than just weight.

Female Athlete Triad

  • Components: Amenorrhea, osteoporosis, energy deficiency affecting health.

  • Importance of adequate nutrition for healthy function and performance.

Conclusion

  • Regardless of body weight, active lifestyles contribute to better health outcomes than sedentary habits.