Nutrition Chapter on Energy Balance

Energy Balance and Body Composition

• Excess energy is stored as fat.
• Fat is used for energy between meals.
• Energy balance is when energy in equals energy out.
• A change in balance causes changes in weight, impacting fat, fluid, and muscle tissue.
• One pound of fat equals 3500 excess kcalories.

Energy In: The kCalories Foods Provide

• Bomb calorimeters measure a food's energy value by measuring the amount of oxygen consumed.
• Oxygen consumption is an indirect measure of released energy.
• Energy is calculated from carbohydrates, fat, and protein in foods.

Food Intake

• Hunger is a physiological response to nerve signals and chemical messengers from the hypothalamus.
• Satiety is the feeling of fullness, signaling to stop eating.
• Satiation is the feeling of fullness, signaling to stop eating.
• Stress eating and external cues like time of day, food availability, and taste, can override hunger and satiety.
• Nutrient composition (protein, low-energy density foods, and high-fiber foods) influences satiation/satiety. High-fat foods are strong satiety signals.

Energy Out: The kCalories the Body Expends

• Thermogenesis is the generation of heat.
• Thermogenesis categories: basal metabolism, physical activity, and food consumption.

Components of Energy Expenditure

• Basal metabolism is about two-thirds of daily energy expenditure.
• Basal metabolic rate (BMR) varies among and within individuals throughout the day.
• Lean tissue is more metabolically active than fat tissue.
• Resting metabolic rate (RMR) is also a measure of energy expenditure. (Factors influencing BMR include age, growth, gender, stresses, environmental temperature, fasting, malnutrition, hormones (gender), smoking, caffeine, and sleep).

Physical Activity

• Physical activity is voluntary skeletal muscle movement.
• It's the most variable component of energy expenditure.
• Factors influencing energy expenditure include muscle mass, body weight, and activity frequency, intensity, and duration.

Thermic Effect of Food

• The thermic effect of food is the acceleration of gastrointestinal (GI) activity in response to food presence.
• This releases heat, and is approximately 10% of energy intake.
• It's greater for high-protein foods compared to high-fat foods.

Estimating Energy Requirements

• Factors influencing BMR include gender, growth, age, and physical activity, body composition, and height and weight.
• BMR declines during adulthood.

Body Weight and Body Composition

• Defining healthy body weight is subjective, often based on perceived image versus actual body size and "ideal" standards, rarely corresponding with health.

Defining Healthy Body Weight (BMI)

• Body mass index (BMI) is calculated by dividing weight by the square of height.
• Healthy BMI ranges from 18.5 to 24.9.
• A BMI over 25 often relates to obesity-related diseases.

Body Fat and Its Distribution

• Information on body fat percentage and distribution is important for disease risk.
• The ideal amount of body fat varies per individual, with common values noted for athletes.
• Central (visceral) obesity, fat stored around the abdomen, may be a stronger risk factor than subcutaneous fat.
• Waist circumference is a good indicator of central obesity.
• Ranges for body fat percentage are included by gender.

Health Risks Associated with Body Weight and Body Fat

• Body weight and fat correlate with disease risk and life expectancy but are not the direct cause.
• Risks associated with underweight include fighting wasting diseases, menstrual irregularities, and infertility, osteoporosis, and bone fractures.
• Risks associated with overweight/obesity include obesity as a designated disease, health risks (cardiovascular disease, diabetes (type 2), inflammation, metabolic syndrome, and cancer), disability, costs (lost work and shortened life expentancy).

Cardio-Respiratory and Muscular Fitness

• Cardio-respiratory and muscular fitness play a vital role in health and longevity.
• Fitness offers many health benefits independent of body weight and is vital.