What's for Dinner? Analyzing Historical Data about the American Diet

Jessica Libertini, University of Rhode Island
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In this activity, students research the historical food consumption data from the U.S. Department of Agriculture to observe trends, develop regressions, predict future behavior, and discuss broader impacts.

Learning Goals

This activity was originally designed for a lower-college-level general education (mathematics for liberal arts - type course), however, the activity can be adjusted for others. This activity can be done in one class session (50 minutes or more), although it can be made longer by tying the results to broader impacts. This activity can be used as an introduction to visualizing and analyzing data in a spreadsheet (e.g. Excel), and/or it can be used to introduce regression. The write-up of this activity is explicitly designed to maximize flexibility by listing a set of potential learning outcomes, and providing a customizable step-by-step guide based on those objectives. See "Description and Teaching Materials" below.

This assignment also includes the following:

Advances students' literacy around sustainability issues.
Encourages self-reflection and personal development of their voice for solving societal challenges
Data analysis, critical thinking, numerical literacy

Context for Use

See first paragraph under learning goals.

Description and Teaching Materials

This activity provides opportunities to cover a broad range of skills, both mathematical and otherwise, depending on your particular needs and focus. Below is a lettered list of learning goals that can be supported through this activity. In an effort to maximize the flexibility of this activity, each element of the step-by-step guide refers back to the lettered learning goals; if you are not interested in covering certain goals, you may choose to skip those steps in the interest of time. Learning goals:
a. Explore and use government reports as a source of data, and how to document the use of these resources;
b. Use Excel (or other spreadsheet) to plot data;
c. Use internal functionality in Excel (or other spreadsheet) to generate linear regressions;
d. Manually (or using technology, but not using built-in functions) calculate a linear regression;
e. Use internal functionality in Excel (or other spreadsheet) to generate non-linear regressions (logarithmic, exponential, polynomial), and be able to determine which style of regression may best fit a particular data set;
f. Use a regression equation and/or graph to make future predictions;
g. Discuss the meaning of their results;
h. Understand how policy changes could impact the results;
i. Engage in a broader discussions about correlations between the findings of different groups and how those results relate to broader systems such as economic, ecologic, and human health issues (synthesizing results);
j. Write a meaningful report of the findings.
k. Give a brief oral presentation of the findings.

Step-by-Step Activity Guide (Note – most steps are optional and/or adaptable!)
1. Provide students with a list of foods and ask them to select one, or assign each student (or small group) a particular food. Note – by assigning these, you insure a more broad set of foods covered.
2. [a] Have students go to the following U.S. Department of Agriculture Factbook in pdf form (see resources below) and retrieve the historical consumption data for their food.
3. [b] Have students enter this data into Excel and generate an x-y scatter plot. (This is a great place to teach some excel tricks for cutting and pasting, or they can simply manually enter the data.)
4. [c,d] Have students generate a linear regression for the data (either on their own or using Excel's built-in functionality).
5. [e] Have students generate other regressions (exponential, etc.) for the data using Excel's built-in functionality.
6. [f] Use regression(s) to predict consumption of that product at some time in the future, perhaps in the year they turn 35. (Note, for some products, like whole milk, it may be negative, which provides a great source of discussion, either as a class discussion, a small group discussion, a paper, or a presentation.)
7. [g w/o e] Discuss results amongst one another or as part of a whole class discussion.
8. [g w/ e] Discuss which form of regression provides the best fit for each food.
9. [h] Ask students if they notice any spots where the trend seems to change (a fit that works well for part of the data but suddenly doesn't fit). Have students think about and discuss possible policy changes or ad campaigns that may cause this sudden shift. (This can also be a great place to introduce piecewise functions!!!)
10. [i] Have a discussion about how these results impact the food system in terms of ecological, environmental, and human health impacts. Some meaningful discussion can stem from noticing that this data is per capita, and that to look at amount, we'd need to consider the population at each of these times as well.
11. [j] Have students write a paper, or a group paper, explaining the project.
12. [k] Have teams of students prepare a brief presentation of their findings.

Teaching Notes and Tips

The activity is designed to be flexible. Users are encouraged to modify this activity to fit their timeframe. Also, if this is the first time your students are using Excel, you may want to provide a handout or some other guidance to get them started. In an effort to promote independence, when students are stuck using software, instead of directly helping them, I encourage them to use the built-in help and/or do an internet search.

Students could then compare their results to some of the latest information on what constitutes a healthy diet and include this in their presentations.


The method of assessment will depend greatly on how you decide to implement the activity. This can simply be done as an ungraded exercise, or it can include a written report or oral presentation. If you are including a written or oral report, think about what communication skills you want to stress to your students, and be sure to provide them a rough outline of your rubric up front, including a breakdown of content versus delivery.

References and Resources