Teaching Sequence

Work through this resource material in the following sequence:

15 mins — Part A: Serving Size Vs Per 100g
10 mins — Part B: Scale Factor
35 mins — Part C: Ranking Sugar Content
5 mins — Reflection

Part A: Serving Size Vs Per 100g

In this part of the lesson, students explore the relationship between the recommended serving size and the per 100g. They find the scale factor between the two, and see how it informs the difference in numbers.

Step 1.

Before class, source different food items to serve as the examples for the lesson. If you prefer, we use some fictional example Nutrition Information Panels (NIPs) below. In order to make the points that we touch on, we recommend that you select one item with quite large servings, such as a cake, and one item with relatively small servings, such as chocolate buttons or small candies that people are likely to eat a handful of at a time.

Step 2.

Explain to students the key features of the NIP for this lesson: the average quantity per serving column, and the sugars row under carbohydrates. This lesson will also deal with the average quantity per 100g column, but we’ll touch on that later: don’t make a meal of it for students right now.

Note: The recommended guidelines from WHO are to limit intake of added sugars to 6 teaspoons a day, or 25g. Because the NIP does not currently distinguish between added and natural sugars, we recommend that you focus on foods that are unlikely to have many natural sugars, so as to make the math as simple as possible. However, it may be worth reinforcing with your students at the end of the lesson that the sugars row is total sugars, including added and natural sugars.

Step 3.

Propose the following situation to students. You have one serving of the cake, and one serving of the small lollies.

Which serve holds more sugar?
In this example, it would be the cake, which contains 22.5g to the 19g found in the lollies. Next, ask:
Which has a higher percentage of sugar?

Talk students through the longer way of solving this problem first. For the lollies, take the 19g of sugar, divide it by the 25g total weight, and multiply by 100 to reach the percentage of sugar. Repeat the same process for the cake. Once you have reached the two sugar percentages (76% and 30% respectively), ask students if they notice anything about those two numbers. They are of course the numbers listed under the ‘Average Quantity Per 100g’ column.

Step 4.

At this point, you can explain the function of the ‘Avg Qty Per 100g’ in more depth. That is, the ‘Per 100g’ column allows you to easily compare different products with different serving sizes. It provides an easy percentage conversion.

Emphasise the difference between ‘Per Serving’ and ‘Per 100g’ by reiterating your earlier questions:

Which product has a higher amount of sugar in total?
Which product has a higher sugar percentage?
Then conclude this part with a class-wide conversation:
In terms of sugar, which product is more unhealthy?

To some extent, this question is debatable. Obviously the cake has the higher amount of sugar per serving, but the lollies are worse for you pound for pound. If you were to eat the same amount of each, the lollies would have two and a half times times more sugar. Whatever students conclude, it’s worth reinforcing these two key points:

Nobody should feel ashamed or embarrassed about what they eat
At the end of the day, the best thing for your health is to keep your added sugar consumption under 6 teaspoons per day, or 25g.

Part B: Scale Factor - Optional

This part is designed to reinforce student understanding of the conversions between the ‘Per Serving’ and ‘Per 100g’ columns. You may choose to expand or shrink this section depending on the capability of your students. This section also draws on material covered in Portion Problems; if you have already completed this lesson with your class, you may only need a quick refresh of the material.

The difference between the ‘Per Serving’ and ‘Per 100g’ columns can be thought of as the scale factor. Commonly, students may work out the difference between the two values and suggest that one is more than the other by a given amount (for instance, by saying that ten is five more than five). Although this method is correct in itself, we want students to figure out the scale factor so that they can understand the conversion between the ‘Per Serving’ and ‘Per 100g’ columns.

Step 1.

Start by demonstrating this formula to students as a way to calculate the scale factor:

For example, if the recommended serving size is 25g, then the equation would be:

100 / 25 = 4

The scale factor would be 4.

Step 2.

After modelling this equation yourself, ask students to calculate the scale factor for one of the products you have explored so far.

Step 3.

Once students have the scale factor, ask them to check it against some of the other figures on the NIP. For instance, if a product had a scale factor of four, then you would expect the protein to be four times higher in the 100g column than in the per serving column.

Note: In some cases, you may find irregularities here due to rounding. Some products prefer to round to 0 decimal places, which can make the ‘per serving’ quantities seem inaccurate, especially when the ‘per 100g’ column already only lists an amount of 2 or 3g. If you come across any instances of this problem in the wild, so to speak, it might be an opportunity to explore rounding in more depth.

Part C: Ranking Sugar Content

In this part, students research their own products, and challenge other students to rank their products from highest to lowest sugar percentage.

Step 1.

Instruct students to get into groups of 3-4 and research the NIPs for a range of different products. We recommend checking the websites of major supermarkets, which often list the NIP information for different products online. They should collect between five and ten products each.

Note: As before, because the NIP does not distinguish between added and natural sugars, our focus is on total sugars - try to encourage students to examine discretionary foods and drinks such as confectionary, soft drinks and sweet biscuits, which are high in added sugars.

Step 2.

Once students have collected their products, they should create a table and list this nutritional information:

The recommended serving size
The amount of sugar (in grams) listed in the recommended serving size column.

Separately, in their workbooks, they should also note the average amount of sugar per 100g serving, and list the different products by the percentage of added sugar they contain.

Step 3.

Once they have created this table, they should swap it with another group. Each group should convert the average sugar per serving into a sugar percentage. They could do this either by dividing the average sugar by the serving size and multiplying by 100, or by dividing 100 by the serving size to get the scale factor and then multiplying the average sugar by the scale factor.

Whichever method they prefer, they should convert the numbers into percentages, and then list the products in order from highest sugar percentage to lowest. Each group should check their answers against those of the original group, and both groups should work together to resolve any disparities. These disparities would provide a great opportunity for students to check their different workings and solve the problem together.

Reflection

Close out the lesson by asking students to reflect on their findings from their research. You may like to use the following questions to guide your reflection:

Did the quantity of each nutritional component present in your product surprise you?
How did this activity make you feel about some of the food that you consume?
What would you like to share?
Where to next?
How are you going to get there?

Teacher Reflection

Take this opportunity to reflect on your own teaching:

What did you learn about your teaching today?
What worked well?
What didn't work so well?
What would you share?
Where to next?
How are you going to get there?

SugarByHalf - Ranking Sugar Percentages

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