1. Begin by asking students to recall what they did in Lesson 1 (they estimated the amount of energy they expended in BMR and physical activities). Then ask, “Where do you get the energy for your activities?”

Students will probably respond that they get energy from food, and this is an accurate response for this question. Food also provides matter for forming new tissues during growth (particularly important for children and adolescents) and repair. However, this is not the emphasis of this curriculum supplement.

Content Standard B:
Energy is a property of many substances.

2. Tell students that in Lesson 2, they will explore how much energy they get from typical breakfast and lunch foods.

In Parts 1 and 2 students will consider serving sizes and calories for typical breakfast and lunch items. In neither case, however, are the foods students consider intended to represent complete, nutritious meals. They merely represent some of the foods that might be included in meals students consume.

3. Organize students into groups of three or four. Give each group a bowl and a bag containing cereal. Ask them to pour an amount of cereal into the bowl that would be their serving for breakfast.

Each should receive a bowl of a different size. Distribute the same kind and amount of cereal to each group, so the only difference between groups is the size of the bowl. Instruct students not to eat the cereal! Students will have to resolve any disagreements they may have about the amount of cereal to pour, perhaps by a compromise between the largest amount and smallest amount preferred.

4. Ask students how many of them drink juice with their breakfast. Distribute a plastic cup to each group and tell students to pour into the cup an amount of water equal to the amount of juice they drink.

Content Standard F:
Food provides energy and nutrients for growth and development.

Distribute a different-size cup to each group. Again, students will have to negotiate about the amount of “juice” to pour into the cup.

5. Ask students how much energy in calories they would have obtained from the two breakfast foods they poured. How many calories were in the cereal and the “juice”?

Students will probably have no idea, but some may suggest that the labels on the food containers will give them the information they need. If no student suggests checking food labels, ask the class where they could find the needed information. This may elicit a response about food labels.

For the cereal, the number of calories per serving will vary. For example, Cheerios and Wheaties each provide 110 calories per serving, while Rice Krispies provides 160 calories per serving. Students may be surprised to learn that granola-type cereals provide about 250 calories per serving. (Given here are calories for cereal only; adding milk increases the calories per serving.)

6. Display a transparency that shows an enlargement of the cereal-box food label and point out the serving-size information and the number of calories per serving.

Students may ask how serving sizes are determined. The serving sizes on food labels are provided by the Food and Drug Administration and represent average quantities usually consumed based on data from national food consumption surveys. However, this information is not relevant to the goal of this lesson. The focus here is that the food label provides the information needed to calculate the calories in the portions of food we actually eat.

The food label provides additional information, such as the number of grams of various nutrients and the percent daily values for several vitamins and minerals. Although this information is not relevant to this lesson, you may want to point out to students the additional information available on food labels.

7. Distribute one copy of Master 2.1, How Much Is One Serving? to each student. Tell students to write the food-label serving size for cereal in column 1 and the number of calories per food-label serving size in column 4.

The food-label serving sizes vary from ½ to 1½ cups, depending on the cereal you use. A serving of Cheerios or Wheaties is 1 cup (1 ounce), while a serving of Rice Krispies is 1¼ cups (about 1.2 ounces). A serving of nugget or granola cereal is typically ½ cup (about 1.9 ounces). Calories per serving vary with the product.

8. Display a transparency made from Master 2.2, Serving Sizes for Various Beverages. Tell students to record the serving-size information for juice in column 1 and the calories per serving in column 4 of Master 2.1, How Much Is One Serving?

Master 2.2 indicates the volume (in cups and fluid ounces) of single servings of fruit juices and the number of calories in several varieties of these beverages. Tell students to use the serving sizes and calorie values for their choice of juice (apple, grapefruit, or orange).

9. Ask, “How can you figure out the number of calories in your servings of cereal and juice?”

Students should recognize that they need to measure the actual amount of food they poured.

10. Provide each group with a dry and a liquid measuring cup and ask the students to measure the amount of cereal and “juice” they poured for themselves.

Students may have to estimate fractional amounts, depending on the measuring cups provided and how they are calibrated. If necessary, students can estimate fractions of a cup.

Tip from the field test: You may want to collect the measuring cups as soon as students have completed and recorded their measurements. This reduces distractions before students begin calculations in the next steps.

Content Standard A:
Mathematics is important in all aspects of scientific investigation.

11. Tell students to record the amounts they measured for each food in column 2 on Master 2.1, How Much Is One Serving?
12. Instruct students to calculate the number of food-label servings of cereal and juice they would have consumed in these breakfast foods by dividing the numbers in column 2 by the numbers in column 1. They should record this number in column 3.

The units for the numbers in the two columns must be the same, such as cups.

Tip from the field test: Many middle school students find the calculations in this and the next steps challenging. You may want to make a transparency of Master 2.1 and display it as you walk through the calculations with the students.

13. Instruct students to calculate the total number of calories in the breakfast foods by multiplying the number of food-label servings they poured (column 3) by the number of calories per serving (column 4). Tell students to record this amount in column 5.

For example, if students poured 1½ cups of Cheerios and 1 cup of “juice,” the relevant portion of Master 2.1 would look like this:

Assessment:
If you wish to use this discussion as a more formal opportunity to evaluate students’ understanding, ask them to write down their answers to the questions. You may then review the responses from each student. Asking students to write down their answers before sharing them with the class allows them to organize their thoughts and reflect on what they have learned.

14. Initiate a brief class discussion by asking, “How did your portion of cereal and juice compare with the serving sizes listed on the food labels?” Listen to several responses, then ask, “Why do you think the amounts of cereal and juice varied from group to group?”

Student answers will vary: some groups may have poured close to a single serving size, while others may have prepared more or less than a serving. Stimulate students to think more deeply by asking the second question. Students will likely respond with answers such as some students were hungrier than others, some students are larger or smaller and require more or less food, or some students don’t like that type of cereal. If no one comments about the different sizes of bowls and cups, ask, “Did the size of the bowl or cup make any difference in the amount you poured?” Why or why not? Affirm all reasonable responses by noting that appetite, size, personal taste preferences, and size of serving containers all affect how much food we consume.

Content Standard A:
Use appropriate tools and techniques to gather, analyze, and interpret data. Some investigations involve making models.

1. Tell students that they will now explore serving sizes of typical lunch foods. Distribute lumps of red and yellow Play-Doh to each group.

Tip from the field test: Make sure that students have more than enough Play-Doh to represent servings of hamburger and cheese.

2. Ask the groups to use the red Play-Doh to make a model of a hamburger patty. This should be about the size they would eat as a single serving.

In both Steps 2 and 3, emphasize that students need not use all the Play-Doh. They should use only the amount they need for their model. If you have students who are vegetarians, tell them to model a “veggie burger.”

3. Ask students, “How many of you like cheeseburgers?” Tell the groups to use the yellow Play-Doh to make a model of a slice of cheese that is about the size they would eat as a single serving.

After making the serving-size slice of “cheese,” students could put it on the “hamburger.” This may give them a better idea of how much cheese is in the slice they see on cheeseburgers.

4. Tell students they will consider milk as another typical lunch item. Distribute a cup to each group and tell students to use their carton or bottle of water to pour an amount of “milk” they would drink with lunch.
5. Display a transparency made from Master 2.3, Cheese and Hamburger Food Labels, and tell students to record the serving size in column 1 and number of calories in column 4 on their copy of Master 2.1, How Much Is One Serving?

For students who prepared “veggie burgers,” the relevant information is 71 grams (2.5 ounces) per serving and 120 calories per serving.

6. Display the transparency made from Master 2.2, Serving Sizes for Various Beverages. Ask students to record the serving size in column 1 and the number of calories per serving in column 4 on the report form for milk.

Students should use the information for the type of milk they usually drink. However, note that using fat-free of low-fat milk is more consistent with the Dietary Guidelines for Americans recommendations for saturated fat intake than is using milk with more fat.

7. Direct the groups to weigh their burger-and-cheese models using a balance and record the weights (in grams) in column 2 of Master 2.1, How Much Is One Serving?
8. Tell students to measure the actual volume of water they poured into their glasses and tell them to record that information in column 2 as well.

Be sure students use their liquid measuring cup for this.

9. Instruct students to calculate the number of food-label servings in their hamburger and cheese models, and the drink volume they chose. They should divide the values in column 2 by the values in column 1 and enter the results in column 3.

Students may be able to complete the calculations here and in the next steps on their own, based on their experience in Activity 1. If necessary, use the transparency of Master 2.1 to walk through the calculations with students.

10. Instruct students to calculate the number of calories in their lunch foods and milk. They should multiply the values in columns 3 and 4 and enter the results in column 5 of their report forms.

If students made hamburgers that weigh 144 grams and a slice of cheese that weighs 56 grams and poured 1 cup of 1 percent milk, the relevant portion of Master 2.1 would look like this:

11. Initiate a brief class discussion by asking, “How did your portion of cheese, hamburger, and milk compare with the food-label serving size?” “What may have affected the size of your hamburger and cheese portions?”

Student responses should be similar to their responses to Step 14 in Part 1 of the activity.

Assessment:
Move around the room and listen to students as they work on this problem. Listen as they explain the source of energy for their bodies (food) and the ways in which that energy is used (BMR and physical activities). This discussion provides an opportunity for students to summarize and reflect on what they have learned.

12. Set up Lesson 3 by asking students to work in their groups to connect the concept they learned in Lesson 1 about the energy they use in BMR and physical activities with the concept they learned in Lesson 2 about the energy they take in from food.

This will likely be challenging for students. Suggest that students use words, pictures, or a combination of words and pictures to show how the energy they take in is related to the energy they use. You can help them by asking, “Why do you need food?” Students will likely respond that they need food for energy for activities such as walking, running, and breathing. Then tell them to show this idea (food is needed for activities) in words and/or pictures.

13. Pair the groups and give them two or three minutes to share their ideas with each other.
14. Display the top part of a transparency made from Master 2.4, The Energy Balance Equation. Point out how this equation is similar to their depictions of the connections between the food they consume and their activities, and explain the terms Energy_in and Energy_out.

Energy_in represents the calories consumed in food, and Energy_out represents the calories expended in BMR and physical activities.

Teacher note: As explained in Information about Energy Balance, E_out also includes the thermic effect of food. Because it represents a relatively small energy expenditure, the thermic effect of food is not included in the lessons in this curriculum supplement.

Content Standard C:
Cells take in nutrients, which they use to provide energy and to make the materials that a cell or an organism needs.

15. Ask students, “What else do children, adolescents, and teenagers need energy for?” After they have responded, fill in the bottom part of Master 2.4, The Energy Balance Equation, with the energy balance equation for children, adolescents, and teenagers: E_in = E_out + E_growth + E_stored

Students may need some prodding to come up with the answer. Ask, “What is a difference between children and adults?” Students will likely respond that adults are bigger than children. Ask, “Why?” and when students respond that children are still growing, you can point out that growth requires energy. Children and adolescents need energy for growth, while adults do not. It is important for this age group to be aware of the extra energy they need to build the new tissues associated with growth and development. They also may not be aware that they store energy as fat for use in growth at a later time. Emphasize that this helps explain some of the diversity in body shapes and sizes, and why healthy bodies come in many shapes and sizes. For children and adolescents, E_in should be greater than E_out until they stop growing.

16. Tell students that they will examine the energy balance equation in more detail in Lesson 3.