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  • Writer's pictureBarbara Mayfield, MS, RDN, LD, FAND

Do your presentations sink or swim? Bring visual aids to the rescue!

Updated: Sep 25, 2023


visual aid using a canister of water and cans of Coke and Diet Coke floating and sinking

What do you think is illustrated with the visual aid depicted in the photo?

Did you guess BMI (Body Mass Index)?


How can I use a visual aid to illustrate BMI?

The visual aid above can be used to illustrate that BMI is an imperfect proxy for body composition.

Similar to underwater weighing, which is used to more accurately determine body composition, these two cans of soda demonstrate that because the composition of their contents is different one floats and the other sinks.

This is how to use it with an audience:

  • Get two cans of soda, one that is regular and one that is sugar-free.

  • Fill a large container with water.

  • Hold up the cans for your audience. Have them notice that the two cans are alike on the outside, they have the same dimensions, they hold the same amount, but they are different on the inside – the liquids they hold are different in composition, just like people of the same height and weight (and therefore the same BMI) can be different in composition.

  • The differences in composition will cause one can to float and the other can to sink.

How does that visual aid help an audience understand BMI?

Your audience may not have experienced underwater weighing, but they probably have gone swimming. People with higher muscle mass sink and people with higher fat mass float.


What does that have to do with BMI? BMI provides a good estimation of body composition, especially when used with population groups. But you can’t use BMI calculations to determine with accuracy an individual person’s body composition. You also can’t determine body composition by someone’s outside appearance.

This visual aid is one I have used multiple times with all types of audiences when explaining BMI. It was shared with me by Pam Estes, MS, RD, a co-presenter for a series of workshops we gave over a decade ago to help health professionals understand BMI. Now, I share it with you.


What other visual aids help to explain nutrition-related topics?

Other favorite visual aids are a lifelike doll when I talk about bonding and attachment, or a golf ball to illustrate the size of a newborn’s stomach when I talk about breastfeeding. I’ve used a Barbie doll and a G.I. Joe action figure when talking about body image and the influence of toys on young children.


Imagine taking these visual aids in your suitcase when flying… it is a sure way to get your luggage inspected!

What are your go-to visual aids? What makes them effective?

That is the topic of our newest tip series: Using Visual Aids Effectively. To download a free copy, go to our tip page.

5 Tips for Using Visual Aids Effectively

Presenters use all types of visual aids to help convey messages. In addition to the props described above, there are images, videos, displays, PowerPoint, and more. Why do we use them? How do we use them effectively? This tip series lists 5 ways…

Tip #1 Use visual aids with purpose

Visual aids are a proven method for capturing and maintaining attention, enhancing understanding and retention of learning, and promoting taking action. To achieve the greatest impact, choose visual aids to meet specific goals. Each one should serve a purpose.


Well-selected and carefully designed visuals enhance communication. Choose them wisely.

Tip #2 Make visuals clear and uncluttered

You’ve heard the saying: “A picture is worth a thousand words.” This statement is true for props, graphics, PowerPoint slides, and all types of visual aids – IF they are clearly conveyed and uncluttered. However, if they are busy and confusing, they will be distracting and ineffective – keep them simple!


As you create visual aids, remember this wise advice… Less is more.

Tip #3 Visual aids illustrate and instruct

Visual aids can illustrate an idea or show a process more efficiently and effectively than a description alone. Imagine trying to explain digestion without an illustration of the digestive tract, or show how to determine stages of ripeness without pieces of fruit or photos?


Adding visual to verbal promotes learning and retention in less time. Illustrate your instruction!

Tip #4 Practice with props

Props are an effective visual aid for many reasons: they can regain attention, illustrate key ideas, enhance understanding, and improve retention. Make sure your props are visible to everyone by using ones that are large enough and displaying them in clear view of your audience.


Prior to use in a presentation, practice with your prop, especially if it is part of a demonstration. Avoid prop failure!

Tip #5 You are the main visual

A common error when using visual aids is putting the focus on the visual aids and not the presenter. When the focus is on your slides or props, you can lose your connection with the audience and reduce your impact.


Keep in mind that YOU are the main visual aid in a presentation – be expressive and purposeful in your movement, gestures, and facial expressions to support your message.

What would you add to this list? What visual aid can you include in your next presentation?

“Well-designed visuals do more than provide information; they bring order to the conversation.” ~ Dale Ludwig


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