Nutrition: Energy Balance and Body Composition

Energy Balance and Body Composition

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

Energy In

• Bomb calorimeter measures a food's energy value.
• It measures the amount of oxygen consumed to determine the released energy.
• The energy from carbohydrates, fat, and protein in food can be calculated.

Food Intake

• Hunger is a physiological response to nerve signals and chemical messengers (hypothalamus).
• Satiation is the feeling of fullness, signaling to stop eating.
• Satiety is the message to not start eating again.
• Stress eating and external cues (time, availability, sight, and taste of food) affect food intake.
• Environmental factors including large portion sizes and favorite foods influence food intake.

Sustaining Satiation and Satiety

• Protein is the most satiating nutrient.
• Low-energy density foods are more satiating.
• High-fiber foods are more satiating.
• High-fat foods provide strong satiety signals.

Energy Out

• Thermogenesis involves heat generation.
• Categories of thermogenesis include basal metabolism, physical activity, and food consumption.

Components of Energy Expenditure

• Basal metabolism accounts for about two-thirds of daily energy expenditure.
• Basal metabolic rate (BMR) varies among individuals and throughout the day.
• Lean tissue is more metabolically active than fat tissue.
• Resting metabolic rate (RMR) is also a component.

Factors Affecting BMR

• Age, height, growth, body composition, gender, stresses, environmental temperature, fasting/starvation, malnutrition, hormones, smoking, caffeine, and sleep all influence BMR.

Physical Activity

• Voluntary skeletal muscle movement is a key component of energy expenditure.
• Muscle mass, body weight, activity frequency, intensity, and duration affect energy expenditure.

Thermic Effect of Food

• The thermic effect of food refers to the acceleration of GI activity in response to food.
• Releases heat, and represents 10% of energy intake.
• Greater for high-protein foods than high-fat foods.

Estimating Energy Requirements

• Factors influencing BMR include: gender, growth, age (BMR declines), physical activity, body composition and body size, and height and weight.

Body Weight and Body Composition

• Healthy body weight definition is subjective, differing from perceived body image vs. actual body size.
• Standards for defining "ideal" body size are also subjective.
• Subjective definitions of healthy weight have little correlation with health.

Defining Healthy Body Weight

• Body mass index (BMI) is calculated by dividing weight by the square of height (kilograms/meters, or pounds/inches).
• A healthy BMI range is 18.5 to 24.9.
• Obesity-related diseases are evident for BMI greater than 25.

Body Fat and Its Distribution

• Important for disease risk.
• Quantifying how much of weight is fat, and where the fat is located.
• Ideal body fat amount varies among individuals.
• Athletes have lower percentages of body fat.

Body Fat Distribution

• Central obesity (visceral fat around abdomen) is a concern.
• Waist circumference is a good indicator of central obesity.
• Upper body fat is more common in men.
• Lower body fat is more common in women.

Fat Percentage

• Different percentages of body fat can be associated with various health conditions (thin to obese).

Health Risks Associated With Body Weight and Body Fat

• Body weight and fat distribution correlate with disease risk and life expectancy.
• Correlations are not the cause of diseases.
• Risks associated with underweight include fighting wasting diseases, hormonal imbalances, and osteoporosis/fractures.
• Overweight/obesity increases risk of cardiovascular disease, diabetes, inflammation, and some forms of cancer. This also increases costs related to lost work and reduced life expectancy.

Fit and Fat versus Sedentary and Slim

• Cardiorespiratory and muscular fitness play an essential role in health and longevity, independently of body weight.
• Fitness offers numerous health benefits.

This quiz covers the principles of energy balance and its impact on body composition, discussing the roles of fat, fluid, and muscle tissue. It also explores concepts of hunger, satiation, and satiety along with environmental influences on food intake. Test your knowledge on how energy is measured and stored within the body.