The Foods We Eat: Find the Fat

FIELD: Life Science DURATION: 45 min.
OBJECTIVE: Students will identify the relative amounts of fat in different foods and food groups.
METHOD: Students hypothesize and test the fat content of different foods using brown paper.
KEY VOCABULARY: Fat, fatty acid. GROUP SIZE: Any


Fat is a molecule present in many of the foods we eat. Fat, together with oils, are the primary energy storage forms for living things. Small quantities of fat in our diet is healthy, however, large amounts can become dangerous by clogging arteries and causing weight gain.

Brown paper bags become transparent when soaked with fat. The amount of transparency depends on the amount of fat.

In this experiment you will use brown paper bag pieces to test for fat in food.

MATERIALS (per group):

Brown paper bag cut into 10+ squares
Sample food items: meat, french fries, apple, carrot, milk, butter


1. Students break into groups if desired.
2. Groups cut bags into 2-inch squares.
3. Label each square with the name of one of the foods.
4. Rub some of each food on the square, or, if it is a liquid, put 3-4 drops on the square.
5. Let the square dry.
6. Hold each square up to a light and put in order of increasing transparency.
7. Find the fattiest foods and the least fatty.


1. FAT RATING: Use a constant light source (such as a small battery and bulb) and a photodetector with meter to measure the amount of light passing through each paper sample. Give each food a numeric value. Average all students' values and create a linear scale showing each food's fat rating.
2. Create a display chart of the food groups with each food ordered by fat content. Think of other foods in each food group, guess their fat content and include in display.

Created April 24, 1997 by Danica Nuccitelli.
Maintained by
Last updated April 24, 1997.