Element 1: Teacher Notes
Metabolism: The total chemical changes that occur during all body activities. This
includes activities of the various organs, regulation of body temperature, and the
processes of tissue growth and repair. The energy output of the body is based on three
demands for our energy: basal metabolism, physical activity, and eating.
Calorie: A measure of heat. The energy value of food is expressed as the number of
kilocalories a specified portion of the food will yield when oxidized in the body.
Kilocalorie (kcalorie): The calorie used in nutritional science and the study of
metabolism is the large calorie (1,000 calories) or kilocalorie. It is used to avoid the use
of very large numbers in calculations.
Basal Metabolism (BMR):
The term basal metabolism refers to the sum of all internal working activities of the
body at rest. Interchangeable terms are basal energy expenditure (BEE), resting energy
expenditure (REE), or resting metabolic rate (RMR).
Most of the body’s energy is spent maintaining these internal working activities. Most of
this energy is used by small but highly active tissues---liver, brain, heart, kidneys, and
gastrointestinal tract. Although they account for less than 5% of the total body weight,
these tissues contribute about 60% of the basal metabolism needs. Resting muscle and
adipose fat are far larger in mass, but contribute less to the body’s basal metabolic rate.
Major Factors Influencing BMR:
1. Lean body mass. This is due to the greater metabolic activity in lean tissues as
compared with fat and bones. The BMR is higher in lean bodies, thus requiring
more energy. It is lower in fat bodies, thus requiring less energy.
2. Growth periods. During growth periods, the growth hormone stimulates cell
metabolism and raises BMR 15% to 20%.
Ages: Birth to 5 years old: Slowly rises 15% to 20%
6 years to puberty: Levels off somewhat
Puberty:
Rises again
Pregnancy:
Rises 20% to 25%
Lactation:
Increases still further than pregnancy
Aging:
Gradually declines
3. Body Temperature. Fever increases BMR approximately 7% for each 1 degree
Fahrenheit elevation.
Cancer, cardiac failure, and respiratory problems also increase BMR due to the
cell activity. BMR rises during cold weather, especially in freezing temperatures,
to generate more body heat. During malnutrition and starvation, BMR is lowered
due to decrease in lean body mass.
Other Factors Influencing BMR:
1.
Physical Activity:
Light activities to heavy activities affect the kcalorie
expenditures. Mental work or study does not require added kcalories. Emotional states
do not increase kcalorie needs, but the energy to compensate for muscle tension or
agitated movements may require more energy.
2.
Eating: Food stimulates our metabolism and requires extra energy for digestion,
absorption, and transport of the nutrients to the cells. It takes about 5% to 10% of the
body’s total energy needs for metabolizing the food we eat.
Taken from: Williams, Sue, Basic Nutrition and Diet Therapy, Mosby-Year Book, Inc. 1995
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Element 1: Teacher Notes
Student Activity Sheet
Calculate your basal energy needs using rounding when doing both
equations.
*Show your work
Equation for daily basal metabolic needs: 1 kcal * kg body weight * 24 hr
Harris-Benedict equation used in hospitals:
Women: 655 + 9.56* weight (kg) + 1.85 * height (cm) – 4.68 * age
Men:
66.5 + 13.8 * weight (kg) + 5* height (cm) – 6.76 * age
For example: A 30 year old woman weighing 150 pounds and is 5’5’’ tall.
1.
2.
3.
4.
5.
6.
7.
1 kg = 2.2 lbs.
150 lbs. ÷ 2.2 lbs. ≈ 68 kg
1 in. = 2.54 cm
5’5” = 65” x 2.54 ≈ 165 cm
655 + 9.56 (68) + 1.85 (165) – 4.68 (30)
655 + 650.08 + 305.25 – 140.4
Answer: 1469.93 basal metabolic rate
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