In small groups, ask students to brainstorm what they know about calories, including what they think a calorie is, examples of high and low calorie foods and whether calories are healthy or unhealthy. In a full-class discussion, go over students’ answers. Introduce the idea that calories are a measurement of energy, and discuss with students what sorts of things their bodies need energy to do: not just activities like running and jumping, but also sleeping, keeping their hearts beating and their lungs working. Discuss with students what happens if their bodies get too many calories -- the excess calories will be stored as fat.
You will need a food item and a calorimeter -- simple calorimeters can be homemade, or bought inexpensively. Show the class the food item you brought with you. Junk food, like chips or cheese curls, often work well. Ask how many of your students like this food, and whether they think that it is low or high in calories. Ask them what that means about the amount of energy the food contains. Now place the food item in the calorimeter, on the nonflammable surface under a beaker of water, and light it. Record the difference between the water’s starting temperature and the temperature it reaches once the food has completely burned. Ask students what this means about how much energy the food contained.
Pass around packages for various foods -- chip bags, cereal boxes, packages for pasta or canned goods. In small groups, ask children to identify the nutrition information on their food item. Once they have done this, ask students to find where the nutrition label lists the food’s calories. List the calories for each item on the board. Ask students if they are surprised by which foods were high and low in calories.
Have students find the carbohydrates, protein and fat on their groups' nutrition labels. Tell the students that these components, called “macronutrients,” contain the food’s calories, and write on the board how many calories a gram of each contains -- four for carbohydrates, four for protein, nine for fat. Ask students to calculate, based on the grams of each component listed, how many calories each provides. Ask your students whether they were surprised by which macronutrient provided the most calories, and discuss with your students the importance of a balanced diet for their health.