Show HN: Which animal shares your body fat percentage?

Note that body fat percentage is notoriously difficult to accurately measure. The linked calculator uses the navy circumference method which gives readings ±3-4 points for most people and even further off for some. It gives me 3.5% which would be insanely low (I'm probably somewhere around 8-10 right now) because I have an unusually wide neck. To get more accurate readings you'd have to pay for a DEXA scan or a bodpod but even those can be off by a couple points.

s_dev · a year ago

My favourite comment on this is the following joke exchange:

Doctor: Your BMI is high I'd like you make some dietary adjustments.

Patient: BMI doesn't measure fat accurately for example professional Rugby players are marked as obese but aren't.

Doctor: Are you a Rugby player?

Patrient: No.

It's a good guideline. Don't let edge cases control your perception and let professionals do their thing with the tools they have -- they're aware of limitations that's why their professionals.

arcticbull · a year ago

While that joke is accurate (although some football players are also obese [1] depending on their position -- Aaron Gibson was 400lbs), BMI was never meant to be applied to individuals. It was designed to be applied to populations. It does a good job of that. Also note that guidelines have historically been created against a very limited selection of race and have not appropriately adjusted for height (although BMI 2.0 corrects the height issues).

If we're just relying on the professional's opinion then they don't really need the BMI, right. They can just look at you and go "huh, you're looking a little thicc today."

BMI is a good tool for population health, a bad tool for individual health, and if it just so happens to correlate to your thiccness then you probably already know that.

I agree with parent that body composition analysis via DEXA or air displacement plethysmography is a far better metric.

I have no doubt that a carpenter can bang a nail in with a screwdriver 90% of the time, that's why they're professionals after all, but when I see it, I can't help but think "there's gotta be a better way mate."

[1] https://www.nytimes.com/2019/01/17/sports/football/the-nfls-...

skrtskrt · a year ago

It is bad all around, the inaccuracies start waaaay before you get to something you could call an "edge case".

I'm 5'11, 180 lb male, that counts as overweight.

I'm 18% bodyfat. You wouldn't even note me as being particularly athletic looking if you walked by, I'm right in the middle of the bell curve for "guy who works out sometimes". There's no way it should be flagging someone like me as overweight.

WaitWaitWha · a year ago

> It's a good guideline.

100% accurate. Caveat Emptor - the world does not understand even the smallest nuance that needs to take into consideration - in this case "guideline".

For example, the US DoD used BMI (DoDI 1308.03) to disqualify a friend of mine from joining. his actual body fat by DEXA? 7%, he was just short and very fit.

kelipso · a year ago

There are plenty of people who do weightlifting or have high muscle density. Probably more than 10% of people and certainly not edge cases. Doctors are basically taught like undergrads are taught, not much critical thinking involved, they just recite whatever is in the relevant document they are supposed to recite from.

teeray · a year ago

If we're going to use imperfect measures for the average Joe, then wouldn't a cheap bioelectrical impedence body fat test be at least a better approximation than jamming height and weight into a formula?

Retr0id · a year ago

GP is not questioning the usefulness of body fat percentage as a statistic (that's its own question), but the crude method of measurement.

It says mine is 1.6%, which I'd say is at least 5% out.

eagerpace · a year ago

I've done a couple DEXA scans recently and they have in fact confirmed that the BMI calculation for me is spot on.

guerrilla · a year ago

> DEXA

Fat calipers would be less accurate than DEXA but much more accurate than Navy circumference method, yet a lot cheaper than DEXA.

loeg · a year ago

Yeah, there are a couple inexpensive midground options here. Calipers is one method, bioelectrical impedance is another.

anon84873628 · a year ago

Yeah, 3.5% would make you leaner than many Mr. Olympia competitors! And nearly at the point of negative health effects.

It's a shame when people use those electronic home scales and believe the results. Someone was so happy to tell me they were at 10% body fat, I could only smile and nod...

Most healthy people would have difficulty dropping below 10-12% without very deliberate effort. And beyond that would probably be kinda freaked out when they start to see all the veins and striations appearing.

foerster · a year ago

I got down to about 6% for a bodybuilding show. It was incredible to look at, but also literally painful to bump into any hard surface, to sit on any hard surface, etc. The amount of bony protrusions you have when the body fat is gone is eye opening. I walk around at 10-13% typically, then lean down for summer and shows.

Most people at 30+ lbs further away from 'having abs' than they think. I see it time and time again.

Mountain_Skies · a year ago

I had a DEXA scan done and for me, it showed higher body fat about five percentage points higher than my scale at home did. But I used that as a calibration point for my home scale. I've found as long as I use the home scale under similar conditions each time, mostly in the morning after voiding my bladder but before showering, that there's not much fluctuation from day to day. If I ever hit my goal on the scale, I plan to go back and get a second DEXA scan.

Two interesting things that also came from getting the scan done was that it showed that I have poor bone density so that's an issue that needed addressing (and hopefully the second scan will show improvement) and the scan was part of a package where they also did a 3d scan of my body exterior, which I was able to download and 3d print. I plan on making a half-and-half model of my body's change upon hitting my goal body fat percentage.

loeg · a year ago

Nearly? 3.5% bf is unhealthy for men and probably dead for women.

wrs · a year ago

Also, when using the Navy method, be sure you read the instructions for how to measure. The “waist” measurement is unfortunately not the number on your trouser size. :)

This is neat!

I have a few thoughts:

- my intuitive sense of animals that are thin or fat is totally off. I think of cows as being fat (ex: "fat cow") but their body fat percentage is only 6%! I think of Gorillas being super fit and muscular but they're at 31%!

- I hate that I can't hit enter after changing the body fat percentage value and have it change

- on that note I'd prefer if there wasn't a "find my match" button at all—after changing the body fat percentage value the match should immediately update

- better than that would be a sliding scale of every animal and the one that matches gets highlighted and centered

- real-world pictures would be better and even better than that would be an image of the animal and a cross section/MRI of the animal where you can see the fat distribution

kelipso · a year ago

Cow is not 6% body fat unless it's been starving or decided to join a body building contest. The source data is bad, probably got the data from ChatGPT.

jayGlow · a year ago

chat gpt gave me 15-25% which seems about right when comparing with other sources.

jaysonelliot · a year ago

It's very fun! The only change I'd make would be to use real photos of the animals instead of the AI images. It's hard to relate to them the way actual pictures would be.

Pexels is an excellent source of free, creative commons images and they have all the animals you need. Here's some geckos https://www.pexels.com/search/gecko/ :)

ramchip · a year ago

I had the same thought. AI art looks cheap, but more importantly it doesn't show if the real animal looks fat or not! Pexels looks super useful.

pimlottc · a year ago

Yeah, fun idea, but the AI-generated animal caricature images are a real turn-off for me.

davio · a year ago

Can also prompt AI to create photorealistic images. Midjourney will probably let you specify famous photographer styles.

lostlogin · a year ago

> Can also prompt AI to create photorealistic images

It can, but the ‘baby peacock’ thing has damped my enthusiasm.

https://news.ycombinator.com/item?id=41767648

I find it sadly ironic that using AI to make images of animals directly contributes to the global warming that is driving those same animals extinct.

n4r9 · a year ago

What was the source video for the data BTW? I'm a little unsure about some of these, like cows having 5% body fat! According to this[0] webpage a "moderate" condition cow has 19% body fat, but it has a "Body Composition Score" of 5.

[0] https://www.grass-fed-solutions.com/body-condition-scoring.h...

tacticalturtle · a year ago

Additionally seals have 40% body fat, but walruses have 20%?

That seems suspicious.

eddd-ddde · a year ago

I didn't know my body fat so I just guestimated 20 to immediately be flashbanged by the image of a walrus.

I consider myself on the skinny side so it was a surprise to be sure.

nradov · a year ago

The body fat content for many animal species varies a lot throughout the year based on migration, food availability, and (sometimes) hibernation. So it depends on when you measure.

ericmcer · a year ago

cows = 5%, wasps = 15%, kangaroos = 2%

I am not an animal expert but just based on intuition this seems off...

cmiller1 · a year ago

nonameiguess · a year ago

I can understand the excitement in principle that you made an app with little effort, but there is no reason this can't be a static page with a table of animals and their average body fat percentages. Users don't need to enter any information and you don't even need a backend. They can simply go the page and find the animal from the table that most closely matches their own bodyfat percentage.

The data is also dubious. I'm not going to enter every possible number to see what comes back, but the number reported here for cows is definitely wrong. Insects have cells that can store nutrients, but not adipose tissue in the familiar mammal sense that we have. There is no way to know how much fat they're actually storing at any given moment versus other nutrients.

timeon · a year ago

Users could still enter the information. But instead of input form it would be browsers 'find in page' search bar.

christiangenco · a year ago

carlgreene · a year ago

I am not 10% BF, but was very surprised to see the African Elephant come up for that!

I'm skeptical of the source data.

ProjectArcturis · a year ago

Source data is very wrong. A walrus is not 20% body fat.

fkyoureadthedoc · a year ago

All of it? How fat is a walrus, where's _your_ source? It probably varies by subspecies, age, season, etc. Maybe they are ripped af under all that blubber?

OP's source is a YouTube video that doesn't list their source. Given that video is post ChatGPT...

6510 · a year ago

It needs to push state the bmi to the url so that I can send it to people.

It could also be fun if one could fill out the age, weight, height and gender to calculate the bmi.

Now that I think about it it would be hilarious to use sliders and have a cartoon person populated with the data generated in real time.