Judith E. Brown

Prof. Albia Dugger • Miami-Dade College

www.cengage.com/nutrition/brown

Calories! Food, Energy, and Energy Balance

Unit 8

Energy!

• Calorie (large Calorie or kilocalorie)• Unit of measure used to

express the amount of energy produced by foods in the form of heat

Bomb Calorimeter

• The caloric value of food is determined by burning it in a “bomb calorimeter”• See Figure 8.2 on page 8-3

The Body’s Energy Needs

• Energy in food fuels body processes • Muscular activity• Growth• Tissue repair and

maintenance• Chemical processes• Body temperature

Three Types of Energy-Requiring Processes

Key Terms

• Basal metabolism• Energy used to support body processes such as

growth, health, tissue repair and maintenance• Assessed while at rest• Includes energy expended for breathing, heart

pumping, maintaining body temperature, and other ongoing, life-sustaining processes

• Uses 60-75% of total calorie needs

Key Terms

• Basal metabolic rate (BMR)• Also called resting metabolic rate (RMR)• Rate at which energy is used by the body at rest• Expressed as calories used per unit of time (hr),

per unit of body wt (kg or lb)

Energy Used for Basal Metabolism

• Men: • BMR calories = body weight (lbs) x 11

• Women: • BMR calories = body weight (lbs) x 10

• Varies ± 20% • Depending on physical activity, muscle mass,

height, health status, genetic traits

Energy Used in Physical Activity

Energy Used in Dietary Thermogenesis

• Dietary thermogenesis• Thermic effect of foods or feeding• Energy expended during digestion of food and

absorption, utilization, storage and transport of nutrients

• Some energy escapes as heat• Accounts for ~10% of total energy needs

Total Calorie Needs

• Estimated total daily calorie needs equal the sum of calories used for basal metabolism, physical activity, and dietary thermogenesis

Calculating Calorie Needs

Energy in Foods

• “Energy nutrients” supply energy• Carbohydrates = 4 calories/gram• Proteins = 4 calories/gram• Fats = 9 calories/gram

• Alcohol also supplies energy• 7 calories/gram

All Calories Count

Calories in Foods

• High-fat foods provide more calories per ounce than foods that contain mostly carbohydrates or protein

Energy in Foods

Calculating Calories

• Nutrient grams x calories/gram = calories

• Example:15 g carbohydrate x 4 cal/g = 60 calories

10 g protein x 4 cal/g = 40 calories5 g fat x 9 cal/g = 45 calories

Total = 145 calories

Calculating Percentages

• Percentages: Divide calories per nutrient by total calories and multiply by 100

• Example:Carbohydrate: 60/145 = 0.41 x 100 = 41%

Protein: 40/145 = 0.28 x 100 = 28%Fat: 45/145 = 0.31 x 100 = 31%

100%

What is the Caloric Value of Foods?

• Most foods are a combination of proteins, fats, and carbohydrates

Energy Density

• Energy density (calorie-density)• Number of calories in a gram of food• Number of calories in a portion of food divided by

the food’s weight in grams

• Example:• 107 calories in 20 grams of potato chips• 107/20 = 5.4

Energy Density

• US diets are high in energy-dense foods• Associated with overeating, weight gain, obesity,

type 2 diabetes

• Energy-dense foods tend to be nutrient poor• Nutrient-rich foods (fruits, vegetables, whole

grains) tend not to be energy-dense

Lower Energy Density

How Is Caloric Intake Regulated?

• Hunger• Physical and psychological sensations that lead

people to acquire and ingest food• Causes weakness, stomach pains, irritability

• Satiety• Feeling of fullness or of having eaten enough

How Is Caloric Intake Regulated?

• Appetite may or may not relate to hunger

• Appetite• The desire to eat• A pleasant sensation aroused by thoughts of taste

and enjoyment of food• Can override hunger and satiety mechanisms

Energy Balance

• Energy balance occurs when number of calories used equal number of calories consumed• Weight is maintained

• Positive energy balance• Calories consumed > calories used• Weight is gained

• Negative energy balance• Calories used > calories consumed• Weigh is lost

Energy Balance