Are you worried that your ostrich or electric eel doesn’t have a healthy body weight? Help encourage health and fitness for animals by calculating their BMI (body mass index)!

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Background:

One widely-used metric for encouraging people to maintain a healthy weight is “BMI” (Body Mass Index), which is defined as BMI = (weight / height²), when given a weight* in kilograms and height in meters.

[*] Or “mass,” for the highly pedantic.

The Issue:

Doctors often recommend that humans maintain a BMI in the 18.5–25.0 range, although the importance of these exact numbers is debated and subject to many edge cases.

Unfortunately, this metric excludes over 99.9% of the world’s total animal population, which are, generally speaking, completely unaware of what a healthy BMI would be.

Materials & Methods Section:

Let’s calculate the BMI of various animals and use this as the start of an educational campaign to help walruses, tigers, centipedes, and great white sharks maintain a healthy lifestyle.

The calculation is simple (Figure 1), but has a slightly complexity: the “height” of certain animals (especially sea life) is not particularly well-defined.

We will define “height” as being the dimension in opposition to gravity: this is intuitive for animals such as the giraffe (“it’s very tall”), but slightly less intuitive for an animal like a snake, which might be 20 feet long but only a few inches “tall.” Nevertheless, this is our methodology!

Fig. 1: Metrics at left were sourced from “the Internet,” and are, presumably, highly accurate. Note that the green anaconda may be 30+ feet long, but is only ~1 foot in diameter, which is considered to be its height in this case. Importantly, not a single one of these species had a BMI that fell in the “normal” or “overweight” category!

As we can see, many animals have a BMI that is substantially outside the recommended 18.5–25 range.

Fig. 2: Consulting the chart above, we see that the man o’ war has a BMI of 0.00018, which falls into the “severely underweight” classification. It would have to gain about 50,000 kilograms (110,000 lbs) to reach a BMI of 19. On the other side of the scale, this elephant has a BMI of 400, and would have to lose ~5,800 kilograms (12,800 lbs) to get its BMI below 30.

Conclusion:

Now that we have these numbers, we can launch an expensive educational campaign (perhaps airdropping educational leaflets into the ocean, forests, and jungles of the world) to let these animals know about BMI.

PROS: Encourages a healthy lifestyle for blue whales and green anacondas, which have historically been under-served by the medical establishment.

CONS: Naysayers might object: “isn’t BMI just an approximation that specifically only applies to humans anyway?” To that, we retort: “does the definition of BMI specifically say that it is inapplicable to an oarfish or giraffe?” Clearly not! Checkmate.