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Big Math and Fries

  • Lesson
Number and Operations
Michael Weingarden
Camarillo, CA

We are lucky to live in an age where there is a lot of nutrition information available for the food we eat. The problem is that much of the data is expressed in percents and some of those percents can be misleading. This lesson is designed to enlighten students about how to calculate percent of calories from fat, carbohydrates, and protein. The calculations are made to determine if a person can follow the Zone Diet with only McDonald's food items.

In this lesson, students pick out a full day's worth of meals from a McDonald's menu with an eye towards the Zone Diet, which specifies percentages of fat, carbohydrates, and protein. The gist of the Zone Diet is that whenever you eat, you should strive to consume 40% carbohydrates, 30% protein and 30% fat. As a result, this diet has also been referred to as the 40‑30‑30 diet.3170 burger fries 

Many sources indicate that an average person requires about 2,000 calories per day. That number varies based on several factors, but is used as the target for this lesson. To prepare for the lesson, you might research some details on the Internet. For example, you can find out what various athletes consume in a day. You will find that it's much more than 2,000 calories. There was an urban legend floating around for a while that Michael Phelps (Olympic swimming gold medalist) was consuming 12,000 calories per day. That turned out to be untrue, but it might be interesting to start things off with a classroom discussion regarding how many calories various athletes consume. That could lead into a discussion regarding whether students know how many calories they consume and what proportion of nutrients are contained in the foods they eat.

Another lesson opener could be the portrayal of diet in the media. Some students may have seen the movie Supersize Me. Discuss the nutritional concerns about eating fast food. This can naturally progress into a discussion of diets. Suggest the idea of being "in the Zone." Ask whether any students have noticed a relationship between what they eat and how they feel. Do they sometimes feel sleepy? hyper? or just right? 

Depending on time, you may wish to have a longer discussion about nutrition. If you choose to do this, you may wish to share the following information on nutrients with students:

  • Carbohydrates: our main source of energy
  • Fats: one source of energy and important in relation to fat soluble vitamins
  • Minerals: inorganic elements that are critical to normal body functions
  • Proteins: essential to growth and repair of muscle and other body tissues
  • Roughage: the fibrous indigestible portion of our diet essential to health of the digestive system
  • Vitamins: important in many chemical processes in the body
  • Water: essential to normal body function, both as a vehicle for carrying other nutrients and because around 60% of the human body is water

In nutrition, some information focuses on food weight and other information focuses on calories. Make students aware of this before they begin the activity to help them avoid errors based on these units. There is not a one-to-one relationship between food weight and calories. The Zone Diet percentages are all with regard to calories, so if you only have weight information, you need to convert to calories to match the Zone Diet percentages.

Fortunately, the conversions between food weight and calories are simple and students may have already studied this information in physical education or health class. Here are the conversions, which are also provided on the activity sheet:

  • Fat: 1 gram = 9 calories
  • Carbohydrates: 1 gram = 4 calories
  • Protein: 1 gram = 4 calories

This information can be written on the board or put up via a transparency.

Hand out the Big Math and Fries Activity Sheet and calculators.

pdficonBig Math and Fries Activity Sheet 

For this lesson, students should use calculators because of the number of calculations required. You can choose how many decimal places that they should round to. Just remember that some of their calculations will be converted from decimal to percent, so they'll need at least two decimal places for those calculations. Students should also be given McDonald's nutrition facts. You can either hand out paper copies or display McDonald's nutrition information via a computer projector (conduct a simple Internet search to find this information).

Have students read the McDonald's nutrition information, and try to pick out enough food so that the total number of calories adds up to 2,000 for the day. It is difficult to meet all the caloric and Zone diet requirements at once, so suggest to students to begin with only one or two. Students can attempt to ensure that their percent of calories from fat for the day is less than 30%. If students can do that, they've done well. Then challenge students who succeed to additional goals, such as keeping carbohydrates to 40% of the total calories and keeping protein to 30% of the total calories. It is difficult to achieve all three, but students should be able to keep fat under 30%. More advanced students may be able to get close to the proper percentage for all three nutrients. When more advanced students finish, have them help slower students who are not finished yet.

A nice wrap-up for this lesson would be to have students that came closest to achieving Zone proportions present their findings and explain how they achieved their results. You might also have students could create posters to present their findings and explain why they would recommend the meal combinations that they came up with.

In the ClassroomSuccessStoryThumb

Read about how the author created this lesson plan. 


Assessment Options 

  1. Ask students to design a single meal and see how close they can get to the 40-30-30 ratio.
  2. Allow students to design a day's meals using any food they choose to meet the Zone Diet. Students should gather their own nutrition information and provide calculations for how they met the diet's restrictions.
  3. Remove the caloric restriction from the activity. Just using the Zone Diet restrictions, is the activity easier, harder, or the same?


  1. Watch the movie, "Supersize Me," with the students and discuss how the movie relates to the lesson. Have students explain whether or not the movie was a fair representation and why. If your students are familiar with sampling and statistical analysis, you may also discuss the experimental model used in the movie.
  2. Talk to a health or physical education teacher and see if they have a unit on nutrition where this lesson could be used as a complement.
  3. This lesson is well suited for a spreadsheet application or a graphing calculator program. A spreadsheet application might take the grams of each nutrient for each desired item and automatically calculate the percentage of calories. Students could then more easily use trial and error to find the desired ratio of nutrients for a particular meal. This is only recommended in a class familiar with spreadsheets or graphing calculators.

Questions for Students 

1. Were you able to stay under 30% for total calories from fat? Do you feel that you designed a healthy day of eating? 

[Answers will vary] 

2. What steps did you take in order to meet the requirements of 2,000 calories total and a 40-30-30 ratio? 

[Answers will vary. What you're looking for are the strategies that students used to try to balance the results. For instance, did successful students focus on one nutrient, get the appropriate percentage and then change one food item to balance the other nutrients? Did they first calculate the total amount of grams needed for each nutrient base on a 2,000 calorie diet and then work backwards? Or did they come up with something new and unique?]  

3. If you were not able to meet the Zone Diet requirements of 40-30-30, could you tweak a few items to change that? If so, which items would you change and how does that improve your carbohydrates-protein-fat ratio for the day? 

[Students should look at nutrient percentages that are too high and try to figure out which items they could remove or replace in order to get better ratios.]  

4. Would it be easier to design one Zone friendly meal and, if so, which items would you choose? 

[Yes, it would probably be easier to design just one meal to meet the ratios. This should lead students to think about balancing nutrient ratios when they go to eat a meal or a snack.]  

5. If you were to design the McDonald's nutrition pamphlet, what would you change from the current design? 

[Answers will vary. One suggestion might be to provide percentage of each nutrient, not just fat.] 

Teacher Reflection 

  • Were most students able to adjust their food choices to achieve Zone proportions? If not, what problems did they run into? How could these problems be avoided?
  • Were any students confused about the difference between calculating the calories due to the nutrient weights and calculating the percent of calories from a particular nutrient? If so, how could this confusion be avoided in the future?
  • Were students motivated to achieve Zone proportions or did they just pick various menu items to get the work part over with?
  • Did students feel that this lesson was interesting or of use to them?

Other Related Resources

Learning Objectives

Students will:

  • Mathematically analyze the food they eat.
  • Identify the relationship between nutrients and the calories.
  • Perform calculations, including percents and conversions.

NCTM Standards and Expectations

  • Work flexibly with fractions, decimals, and percents to solve problems.
  • Understand and use ratios and proportions to represent quantitative relationship.
  • Develop, analyze, and explain methods for solving problems involving proportions, such as scaling and finding equivalent ratios.

Common Core State Standards – Mathematics

Grade 7, The Number System

  • CCSS.Math.Content.7.NS.A.3
    Solve real-world and mathematical problems involving the four operations with rational numbers.

Common Core State Standards – Practice

  • CCSS.Math.Practice.MP1
    Make sense of problems and persevere in solving them.