BioEd Online

Teacher Background

Energy fuels growth, movement and all the processes in every cell inside the body. It has many different forms and cannot be created or destroyed, only transformed from one form to another. Both light and heat are examples of energy.

Many students may have difficulty understanding energy and its measurement. One way to approach these concepts is to think of energy as the ability to make either a change or a movement. There are many ways of making a change or creating movement, and energy can have many forms. For example, when a person kicks a ball, the energy from the kick makes the ball move forward. Or in cooking, energy in the form of heat changes an egg white from a clear liquid to an opaque solid. Energy in food commonly is measured as calories.

The easiest way to describe calories is to introduce them as a unit of measure. Weight can be measured in kilograms or pounds; distance can be measured in meters or feet; and energy can be measured in calories. As shown in the "Energy Sources" activity, one calorie is the amount of energy necessary to raise the temperature of one milliliter of water by one degree Celsius. Usually, when we refer to calories in food, we actually are considering kilo­calories. One kilocalorie equals one thousand calories and usually is written in the capitalized form, “Calorie.”

In this activity, students will figure out how many Calories a typical teenager needs every day. Baseline Calorie needs (also called Basal Metabolic Rate, or BMR), can be estimated based on gender, age, height and weight. Each student also may calculate his or her own baseline Calorie needs (see Step 6).

Objectives and Standards

Life Science

• All animals, including humans, are consumers, which obtain food by eating other organisms.

Physical Science

• Energy is a property of many substances and is associated with heat, light, electricity, mechanical motion, and the nature of a chemical. Energy is transferred in many ways.

Science in Personal and Social Perspectives

• Food provides energy and nutrients for growth and development. Nutrition requirements vary with body weight, age, sex, activity, and body functioning.

• Regular exercise is important to the maintenance and improvement of health. The benefits of exercise include maintaining healthy weight.

Science, Health and Math Skills

• Calculating

• Predicting

• Converting measurements

• Drawing conclusions

Materials and Setup

Materials per Student

• Calculator

• Copies of student sheets (see Lesson pdf)

Setup

• Have students work individually

Procedure and Extensions

1. Begin a class discussion of energy by asking questions such as, What is energy? Where do we get our energy? What do we do with the energy? Do we all need the same amount of energy? What happens to the food we eat? Tell students that they will be investigating how many Calories adolescents need every day. Explain that “calorie” is a measure of energy that can be applied to food.

2. Give each student copies of the two activity sheets and have them follow the instructions to calculate the daily Calorie needs of an average teenage boy and girl.

3. Students may need assistance with metric measurements, such as kilograms (kg) and centimeters (cm), necessary for their calculations. If appropriate, talk about conversion factors and different measurement systems. One kg is approximately 2.2 pounds (lb) and one cm is 0.4 inches (in.).

4. Discuss students’ calculations. Mention that a person’s energy needs are based not only on gender, weight and height, but also on daily activities. Explain that Basal Metabolic Rate (BMR) represents the amount of Calories necessary to maintain life. Ask, What are the differences among caloric requirements of different physical activities?

5. Expand the discussion by introducing the idea that athletes and other persons who are physically fit spend more Calories and as a result require more Calories. Help students understand that to stay fit and healthy, a person must maintain a balance between the intake and expenditure of Calories.

6. As a take-home activity, give students clean copies of both activity sheets and have them calculate their own BMRs and total daily Calorie needs.

Handouts and Downloads

Download color images from The Science of Food and Fitness Teacher's Guide.