Fat Finders

Kottie Christie-Blick

Winston Christie-Blick

Every day the media bombards us with concern over childhood obesity. More American children than ever before are developing health problems related to their eating habits and lack of exercise. The classroom is the perfect place to deal with this national crisis by speaking directly to our children.

That’s why I decided to focus on teaching students about fat in food. If children could become more aware of the fat in foods they eat each day, they could better control how much weight they gain or lose. I wanted students to understand that all bodies need some fat, and that eating certain types of fat is healthy for the body, but eating too much of the wrong type of fat can cause the body harm. I also wanted to inspire students to think about their food choices and the effects these choices have on their body. I created the following science lessons for my fourth graders, but they could easily be adapted for younger or older students.

Serious About Fat

I began the lessons by sharing with students what I had been reading in the newspapers and hearing on TV about obesity among children: “There is a national health concern that too many American children are overweight. Scientific studies tell us that part of the problem is that today’s children are eating too much fatty food. They are also eating too much sugar and not getting enough exercise. I think if kids understand the problem and can figure out some solutions, then they can control their own health—that’s powerful, don’t you think? So, let’s do some activities to learn more about fat.”

I asked some key questions to lead the children to think about fat in a serious way:

• Where does fat come from? (Animal and plant fats were discussed briefly.)
• What does it look like? (Children described white, bouncy globs attached to meat and the grease on their fingers after touching certain foods. A few mentioned the liquid oil they had stored in their kitchen cabinets, but nobody thought of butter or margarine as fat.)
• Why is it worthwhile spending our time looking at the fat in different foods? (We know that people who want to stay healthy and full of energy don’t eat too much fatty food. Some fat is good for us to eat, but when we eat too much fat, the body can’t use it all and it turns the extra into body fat. Some body fat is good, but when the body starts making too much fat it can become “overweight.” That’s not good for the body.)
• How do you know which foods are high in fat? (A few students knew to look at product labels. Most said to just look at the food and see if it looks greasy.)
• How could you compare different foods to see which has the most fat? (I reminded students about what we’ve done in the past when we wanted to find answers—perform an experiment so we can see the results for ourselves.)

Grease Marks the Spot

Explore the topic of Nutrition

Delta offers a brilliant experiment called “The Fat Test” in its Food and Nutrition Module (see Internet Resources). It compares the different amounts of fat in foods by calculating the area of the grease spot each food leaves behind on brown paper in a way that even a very young child can understand. To lead the students to this experiment, I held up a piece of a brown grocery bag, cut 13 cm × 13 cm. I asked what would happen if they put a piece of greasy food on it. Most of the children knew that it would leave a grease spot (as the fat moves through the paper it darkens the fibers). How could we compare the fat content of different foods? Using this cue, and sensing a hands-on activity coming up, the children responded enthusiastically, suggesting that they put different foods on brown paper and then compare the size of the grease spot left behind. We decided this would help us see which foods were greasier than others.

However, there was a problem. How could we make sure the test was fair to all of the foods? What if Connor puts more food on his paper than Alissa, and it leaves a bigger grease spot? Does it really have more grease? What if Meghan spreads her food out on the paper and Marlon piles his high? What if Lizzi examines her results in one day and Olivia examines her results after two days? Is it fair?

To settle these concerns, the children were reminded that in order to perform a good experiment they would need to hold the variables not being tested constant. That is, everything except the one thing being tested would need to stay the same. Because they wanted to compare how much fat there is in different foods, they’d need to use different foods. Everything else in the test would stay the same. They would need to use the same amount of food each time and put it on the paper the same way; leave it on the paper the same amount of time; and use the same kind of paper for each food sample.

The children excitedly donated a bit of their lunch “for science,” while I made sure there were both fatty foods and low-fat foods in the samples. I knew that bologna, salami, hamburger, peanut butter, cheese, chips, cookies, and butter would work well for the fatty foods. Bread, crackers, rice, fruits, vegetables, and low-fat yogurt would work well for the low-fat/nonfat foods.

Be aware of any student food allergies when selecting samples, especially allergies to peanuts. Some allergic children are all right if they don’t work with the troublesome food. Others are so sensitive they can’t even be in the same room with the food.

Scientists at Work

The students worked hard to be scientific in their procedure. They tried their best to be accurate in their measuring, to be fair to all the foods, and to be honest when reporting their results. If someone were to repeat their procedure they knew that this person should get the same results as they did.

Working with a partner, each pair chose one of the food samples. They drew a circle, 6 cm in diameter, on a 13 cm square of brown paper. (I cut out cardboard templates ahead of time for them to use as a guide to make the job quick and easy.) Students weighed 1 g of the food using a pan balance, so everyone would be comparing the same amount of food. To do so, they placed the prepared paper on one side of the scale and a blank square of brown paper on the other side to balance. Next, they placed a gram mass on one side and added bits of food on the other side, inside the circle, until the balance was level. They removed the test sample and paper from the scale and pulverized the food with the back of a spoon or spread soft foods with a Popsicle stick, completely covering the inside of the circle so that each food was spread on the paper in the same way.

After labeling their food samples, students put them on the science table for the weekend so the water in the food could evaporate. Water also darkens the fibers of the brown paper and might be mistaken for grease. The fat stain would be left behind, as it doesn’t evaporate. The children left school that day excitedly predicting which foods would leave the biggest grease stain.

On Monday morning, the children rushed to the science table to see the results. With lots of comments such as, “Look at all the fat that came out of the bologna! That’s gross!” and “The cracker didn’t make any grease stain,” I knew the lesson was making an impression. They were eager to begin science class that day to talk about their observations.

The Results Are In

The children were reminded that they had performed an experiment to compare the different amount of fat in foods. This information could help them make healthy decisions about how much and what kinds of food to eat for a healthy diet.

To allow for easy comparisons of grease stains, the children would use a centimeter grid copied onto a transparency sheet to determine the area of each grease stain. Using an overhead projector, I demonstrated the process and then showed students how to write the answer in centimeters squared (e.g., 36 cm²).

Partners worked together to figure out the area of a stain in square centimeters. After scraping off the excess food from their piece of brown paper, they placed the transparency grid on top of the paper and counted the number of squares covering the stain. We agreed that if at least half of the square had grease in it, it would be counted. Using a marker to put a dot on each square they counted helped students keep track.

Gathering together on the rug as they finished, each group recorded its food and the area of the grease stain on a large chart for all to see. They read their results out loud (e.g., “One gram of cheese doodles left a grease stain 105 cm²”). At the conclusion, we ranked the food by size of grease stain, numbering foods from 1 to 12, with 12 being the food that left no grease spot on the paper.

Looking at the chart and asking a simple question, such as, “What have you learned from this experiment?”, yielded both simple and insightful responses. Some students simply shared comparisons of fat levels from reading the chart. Others commented that they hadn’t known that some of the foods (e.g., bologna and peanut butter) were “fatty” foods. Some of the children said they were “grossed out” to see all the fat in chips. One student wondered if the salt in many “junk foods” had any effect on the fat in those foods.

Making Connections

When asked to connect what they learned from this experiment and what they already knew about “junk food,” students began using science to understand the big picture. Using a think-pair-share format, the students were asked to stretch their understanding through writing and discussion. First, they wrote their connections individually in pencil. Then, for 10 minutes they discussed their answers with their partners, adding ideas gleaned from their partner in blue pencil.

Afterward, we had a class discussion. Students shared their best answers with the whole class: “I see that potato chips have a lot of fat in them. If I eat too many of them my body can’t use all the fat, so I could gain weight. That must be why potato chips are considered a ‘junk food.’” Hearing students connect what they learned to previous knowledge and then draw conclusions about healthy eating demonstrated that powerful learning was taking place. Reading their written insights gave me a clear understanding of which individuals understood the message about how to make healthier food choices.

Concluding, I reminded the students that some fats are good for the body, such as the ones found in vegetables, fish, and nuts. Eating too much of the animal fat found in meat and dairy—“saturated fat”—can cause heart problems and some cancers. On the other hand, these are good foods to eat because meat is high in protein for strong muscles, and cheese is high in calcium for strong bones. The important thing is to have a balanced diet. The more one learns about what’s inside food, the more one can make good decisions for a healthy body. We also discussed how frying foods in fat to make them crisp turns healthy foods into fatty foods because the foods absorb the fat and then we eat the fat (e.g., fried chicken, French fries, and chips). People who make healthy decisions for themselves don’t eat many fatty foods.

Excess sugar in one’s diet is also a cause of obesity, of course, but I thought it best to focus the student’s attention on one area. I did address these concerns later in the unit when I taught students how to read nutrition labels.

Sharing the News

The next day, when reviewing what the students had learned about fat in food, I asked them why this was important to know. The children now understood that not knowing about fat in food could be harmful to your body because then you might eat too much fatty food, causing you to become overweight or increasing your chance of illnesses. We agreed that this was really important. I explained that when scientists discover important information, they share it with others. The children agreed that the information they had been learning was so important they should share it.

In order to disseminate their results about fat in food, the students used the data from the “fat test” chart to create poster-size bar graphs. They included messages on them such as, “Know what you’re eating,” and “Compare the fat!” to grab attention and send their message home. As they finished their posters, they examined their graphs and wrote three comparison statements in their science logs, such as, “One gram of Cheetos has more fat than one gram of Doritos.”

In addition to reinforcing the message that different foods—even different “junk foods”—contain different amounts of fat, this activity allowed me to assess students’ ability to read a chart and create a bar graph. After checking each other’s comparison statements for accuracy, the children hung their graphs around the school, putting several in the cafeteria for children to read and discuss over lunch.

These activities allowed the students to experience the entire scientific process: creating a question, discovering an answer through experimentation, recording data on a chart and converting it to a graph, discussing their results with peers, and disseminating their findings to others. During our final group discussion, the children told me what they had learned over the past two weeks. I was pleased to hear that students understood that knowing the fat content of food allows them to make healthier decisions about how much and what kinds of food to eat. Further, students realized that they could use science to help them make choices that affect their lives. Powerful learning, don’t you think?

Kottie Christie-Blick (kottie@optonline.net) is a fourth-grade teacher at Cottage Lane Elementary School in Blauvelt, New York.

Resources

National Research Council (NRC).1996. National science education standards. Washington, DC: National Academy Press.

Internet

Delta Education Food and Nutrition Module
www.delta-education.com/productdetail.aspx?
Collection=Y&prodID=1086&search=nutrition

Click here for PDF file.