The Concept of Energy Balance

Energy Balance: The relationship between energy intake (from food and beverages) and energy expenditure (through basal metabolism, physical activity, and thermic effect of food).

Positive Energy Balance: When energy intake exceeds energy expended, leading to weight gain. This can occur during:

• Pregnancy

• Childhood

• Adolescence

• Increased muscle mass or adipose tissue

Negative Energy Balance: When energy expended exceeds energy intake, leading to weight loss. This can occur due to:

• Reduced food intake

• Increased physical activity

• Loss of fat, muscle, glycogen, or water

Measuring Energy Intake

Kilocalories in Food:

• Measured using a bomb calorimeter, which provides physiological fuel values.

• Nutrition analysis software or food composition tables can also be used.

Kilocalories per Gram:

• Carbohydrates: 4 kcal/gram

• Protein: 4 kcal/gram

• Fat: 9 kcal/gram

• Alcohol: 7 kcal/gram

Measuring Energy Expenditure

Components of Energy Expenditure:

• Basal metabolism

• Thermic effect of food (TEF)

• Thermic effect of exercise (TEE)

• Adaptive thermogenesis

Total Daily Energy Expenditure (TDEE): Total kilocalories needed to meet daily energy requirements.

Basal Metabolic Rate (BMR): Energy spent to meet the body's basic physiological needs.

• Influenced by factors such as lean body mass, age, gender, body size, genes, ethnicity, stress, thyroid hormone levels, nutritional state, environmental temperature, and caffeine/nicotine intake.

Resting Metabolic Rate (RMR): Often used instead of BMR as it is easier to measure.

Thermic Effect of Exercise (TEE): Energy expended during physical activity.

• Depends on the activity type, duration, and body weight.

Non-Exercise Activity Thermogenesis (NEAT): Energy expended from activities not considered exercise.

Thermic Effect of Food (TEF): Energy used to process macronutrients and extract kilocalories from food.

• Accounts for about 10% of kilocalories consumed.

• Higher for protein than carbohydrates or fats.

• Influenced by nutrient type, meal composition, alcohol intake, age, and athletic training status.

Adaptive Thermogenesis: Body's regulation of heat production in response to environmental changes (stress, temperature, diet).

Measuring Energy Expenditure

Direct Calorimetry: Measures energy expenditure by assessing body heat loss within a metabolic chamber.

Indirect Calorimetry: Estimates energy expenditure by measuring oxygen consumption and carbon dioxide production.

Simple Calculations: Used to estimate total energy expenditure based on age, gender, height, weight, and physical activity level.

• Estimated energy requirement (EER)

• Harris–Benedict equation for RMR

Body Composition

Body Composition: Ratio of fat tissue to lean body mass (muscle, bone, organs).

• Expressed as percent body fat.

• Important for assessing health risks related to body fat.

Types of Body Fat:

• Essential fat: Necessary for body functions. Higher in women (12%) than men (3%).

• Stored fat: Found in adipose tissue (subcutaneous under the skin and visceral around organs).

Adipose Tissue: Releases fat during negative energy balance (weight loss) and accumulates fat during positive energy balance (weight gain).

Brown Adipose Tissue (BAT): Specialized fat cells that generate heat, contain more mitochondria, and rich in blood.

Body Fat Distribution

Central Obesity (Android Obesity): Excess visceral fat in the abdomen, increasing risk for heart disease, diabetes, and hypertension.

Gynoid Obesity: Excess fat around the thighs and buttocks, more common in women.

Assessing Body Composition

Hydrostatic Weighing: Assesses body volume by underwater weighing (2-3% error margin).

Air Displacement Plethysmography (BodPod): Measures air displacement (3% error margin).

Dual-Energy X-ray Absorptiometry (DEXA): Measures bone density and body mass (1-4% error margin).

Bioelectrical Impedance Analysis (BIA): Measures resistance to low-energy current through muscle and body fat.

Skinfold Caliper: Measures fat in various locations, accurate with trained technicians.

Waist Circumference: Indicates health risk, >35 inches in women and >40 inches in men indicates increased risk.

Estimating Healthy Body Weight

Height and Weight Tables: Provide a healthy weight range based on height, gender, and frame size. Less commonly used now.

Body Mass Index (BMI): Calculates body weight in relation to height.

• Used to screen for disease risk.

• Obese individuals have a higher risk of premature death.

• Not always accurate for athletes, older adults, or individuals less than 5 feet tall.

Health Risks Associated with Body Weight

Underweight: Increases risk of anemia, osteoporosis, heart irregularities, amenorrhea, depression, anxiety, infections, temperature regulation issues, and premature death.

Overweight: Increases risk of heart disease, hypertension, stroke, gallstones, hyperlipidemia, sleep apnea, reproductive problems, and certain cancers.

Disordered Eating

Disordered Eating: Abnormal and potentially harmful eating patterns, such as refusing to eat, compulsive eating, binge eating, restrictive eating, vomiting, and abusing diet pills.

Eating Disorders: Psychological illnesses with specific criteria, including anorexia nervosa, bulimia nervosa, binge eating disorder, orthorexia, and night eating syndrome.

Anorexia Nervosa: Characterized by self-starvation, excessive weight loss, fear of gaining weight, and health consequences like electrolyte imbalances, hair loss, and nutrient deficiencies.

Bulimia Nervosa: Characterized by binge eating followed by purging, with health consequences such as esophageal tears, tooth decay, and electrolyte imbalances.

Binge Eating Disorder: Characterized by recurrent binge eating without purging, leading to health issues like high blood pressure and heart disease.

Orthorexia: Obsession with healthy eating, often leading to restrictive diets and potentially developing into anorexia.

Night Eating Syndrome: Eating a majority of daily kilocalories after the evening meal and during the night, often associated with low self-esteem, depression, and stress.

Treating Eating Disorders

Multidisciplinary Approach: Involves psychological, medical, and nutrition professionals. Treatment includes meal planning, food journals, identifying triggers, and recognizing hunger and fullness cues.