An animal obesity epidemic?

August 8, 2013 6:18 PM

In a remarkable paper Allison et al. (2011) gather data on the weight at mid-life from 12 animal populations covering 8 different species all living in human environments. Dividing the sample into male and female they find that in all 24 cases animal weight has increased over the past several decades.
posted by bookman117 (34 comments total)

It continually blows my mind that people don't understand what their pets (and in my case I mean mostly cats, the obligate carnivore pet) need nutritionally to be healthy.

Also, dry food is a lot easier on the owner than wet food and much more caloric-ly dense. Mary Roach's GULP has a pretty funny section on how pet food sellers create and test their food for maximum pet likability among both human and pets.
posted by OnTheLastCastle at 6:39 PM on August 8, 2013

Did you read the article? This effect was measured in animals that aren't pets, too.
posted by ocherdraco at 6:44 PM on August 8, 2013 [9 favorites]

I heard about this study a while back, and it really influenced my opinion of the obesity crisis. This is important science.
posted by painquale at 6:46 PM on August 8, 2013 [1 favorite]

I've read that the same sort of general weight increase exists in lab animals, making for speculation that a virus is involved...
Now I'll go read the link and see if I'm being redundant.
posted by cccorlew at 6:46 PM on August 8, 2013

This article, by David Barreby, is where I first heard of the study. It's a really interesting article that was unfortunately deleted when posted to Metafilter. It's worth reading.
posted by painquale at 6:51 PM on August 8, 2013 [6 favorites]

And I am....
posted by cccorlew at 6:51 PM on August 8, 2013

Oh, I missed that it was linked in the Marginal Revolutions post. Still, it's a great article!
posted by painquale at 6:52 PM on August 8, 2013

He ain't heavy, he's my terrier.

OK, he' is also overweight.
posted by filthy light thief at 7:16 PM on August 8, 2013 [3 favorites]

Someone needs to go tell those animals about the laws of thermodynamics and how it's as simple as calories in and calories out.
posted by Ghostride The Whip at 7:35 PM on August 8, 2013 [21 favorites]

I read the article. I can still talk about people not knowing how to feed their pets properly.
posted by OnTheLastCastle at 7:46 PM on August 8, 2013 [1 favorite]

Sounds like a minor Night Vale plot point. "Sources report that gravity seems to be slightly stronger today than it was yesterday. Also, a throbbing vibration has been emanating from the dog park..."
posted by echo target at 7:46 PM on August 8, 2013 [4 favorites]

The aeonmagazine article that painquale linked to is really good, and comments are entertaining. It really is amazing how strongly thin people like to cling to the belief that they are thin because of their moral superiority and self-discipline, even in the face of scientific evidence

And I've always thought there is far more going on in weight gain and loss than "thermodynamics". The calorie balance required to maintain a steady weight in the face is so incredibly fine that there is clearly far, far more going on than 'feeling full'. Your stomach isn't calculating the calorie density vs volume of the food you are eating, and it's not reading a pedometer and a thermometer to determine how much energy you expended. For that matter, it's become extremely clear that depending on your microflora and other factors, you can extract wildly varying amounts of calories from the exact same food.
posted by tavella at 8:10 PM on August 8, 2013 [6 favorites]

Related to rising CO2 levels?
posted by bottlebrushtree at 8:53 PM on August 8, 2013 [1 favorite]

bottlebrushtree: I was wondering if it might be something like that. I sort of hope it isn't because it seems pretty clear that situation is going to keep getting worse for quite some time.
posted by aubilenon at 9:30 PM on August 8, 2013

My pet theory/lunatic-rant is bovine hormones in dairy and beef production.

Captured mice/rats could be benefiting from the trickle-down from human food. Pet food is made mostly from industrial meat byproducts, and hormone use is widespread in the USA in those sectors as well. Lab animal food is likely to be within the same supply chain, rat chow isn't made from organic hand-grown grass-fed free-range beer-massaged unicorn meat byproducts.

My other rant is widespread antibiotic use in all sectors of the meat industry and human health. That too may trickle down and kill of certain populations of symbiotic intestinal flora, and what's left is more efficient at releasing nutrients (energy, mostly) for our gut to absorb or the continuous de-floration produces a bunch of dead bacteria which we then soak up as energy when otherwise the bacterial population reaches an equilibrium instead of going through cycles of mass die-offs and exponential growth. One reason antibiotics are used to increase ruminant weight gain but this is mostly a cellulose energy conversion pathway thing and most of don't consume enough cellulose for this to be really significant nor do we have compartmented stomachs.

I'm a fan of the "calories in calories out" theory - but it has to be complicated by the input/output of the intestinal microfloral landscape. If you have populations of gut bacteria that are good at soaking up energy that your gut can absorb and also good at being pooped out, then that's a weighting in on the "calories out" end. Even if they're gut-resident, the intestinal microflora will reach a shifting equilibrium - they're mostly happy but not overfed so they don't feel like they have to divide quite so fast and are ok existing instead of spamming out clone-ish children with some mutations. If you have populations of gut bacteria that are good at converting stuff that your digestive system can't handle (which is a lot) and that population is prone to mass die-offs, which releases all that nutritional energy for our intestines to absorb followed by exponential growth until the next mass die-off, that's a lot more "calories in" that should have been "calories out."
posted by porpoise at 9:34 PM on August 8, 2013 [4 favorites]

In many cases it is as simple a matter as getting up off your own fat ass and taking the fucking dog for a walk. Taking a dog for a walk is probably the single best thing a human being will ever have the pleasure of doing and I'll never understand why people who have dogs aren't out in the streets and the fields and the parks and the gardens and the riverbanks just fucking walking them non-stop, just everywhere all the time.

What I'm saying is a lot of the world's problems get solved when you take your dog for a walk.
posted by turbid dahlia at 9:45 PM on August 8, 2013 [3 favorites]

Come on - everyone knows it's due to the Expanding Earth.

Seriously though, this is interesting. I do think there's *something* going on. Frankly, I wouldn't be surprised in the least if there was a complex etiology happening where multiple sources play a role. Something like GMO or chemically processed foods in some manner (I am *not* an anti-GMO nut, btw), combined with plastics potentially altering our hormones, processed foods (HFCS and such?) having a different process of metabolism (this, to me, is an open question, and I don't fully believe there is a full resolution on HFCS, I've heard both sides of the argument on HFCS and I think the jury is still out on this one).

And now someone posits CO2? Hmm... That's certainly in interesting tack.
posted by symbioid at 10:15 PM on August 8, 2013 [1 favorite]

Fun Fact: There is a research animal food factory a few miles from where I live. On my way to work I can tell when they are operating their processes (whatever nature those may be) when I smell what apparently is monkey chow.
posted by symbioid at 10:19 PM on August 8, 2013 [1 favorite]

Terrific. Global Fattening.
posted by webmutant at 10:21 PM on August 8, 2013 [1 favorite]

Here's my wild guess: improved climate control? Animals burn fewer calories when it's a pleasant 70 F year-round.
posted by Pruitt-Igoe at 10:47 PM on August 8, 2013 [1 favorite]

Seems like you could test the CO2 hypothesis (at least partially) by looking for changes in the weights of truly wild animal populations (ones whose diet doesn't involve human refuse/processed foods in any way). That would at least rule out (or rule in) a lot of more directly human-related factors, like bovine growth hormones or antibiotics or what-have-you. I guess the question is, does anybody have records, from catch-and-release animal tracking programs or the like, of what various populations of wild animals used to weigh?
posted by mstokes650 at 11:09 PM on August 8, 2013

I am *not* an anti-GMO nut

Wait, being anti-GMO is nutty now?
posted by This, of course, alludes to you at 1:28 AM on August 9, 2013

Data seems to be limited to USA only. Would be interesting to have an international comparison.

I don't see how lab animals weight going up is surprising. Lab people surely don't cook meals for the animals and whatever changed in pet food, changed in rat food.

Found this from Lab Animal Europe Magazine: "He further adds that in Europe, rodent diets are more in line with the nutritional needs of the animals, whereas in the US, people tend to overfeed protein."

also

"But along with the explosion of choices in pet foods, including different sizes, shapes, colors, flavors, textures, ingredients and ingredient qualities, there is now a plethora of chows and other foods for most laboratory animals, even exotics."
posted by Marauding Ennui at 2:25 AM on August 9, 2013

We live in a society of relative abundance. It seems perfectly reasonable that animals around us are going to "benefit" from that abundance.
posted by gjc at 3:53 AM on August 9, 2013 [1 favorite]

As I said a week or two ago when we last discussed this study:

It seems like a perfectly respectable paper, but it's still just a single study. It's got a tremendous amount of media attention, and is regularly trumpeted as evidence that Something Mysterious is Going On. But there are other explanations:

Jaap Seidell, a nutrition and health researcher at the VU University Medical Center in Amsterdam who has studied the link between weight gain in pets and their owners, contends that the data presented in the study could be explained by lifestyle factors.

"This is an interesting collection of data, but it's very difficult to interpret them," Seidell says. Pets and feral animals might very well be subject to changes in our eating patterns, and there isn't enough information to conclude that the captive animals are exempt from such influences, he adds. Other factors may also have changed. For example, over the past 30 years the number of rodents housed in each cage may have altered -- which could very well affect the amount of exercise they get.

It's not exactly hot news, this study gets mobility-scootered out in every obesity thread.
posted by TheophileEscargot at 5:25 AM on August 9, 2013 [3 favorites]

I don't see how lab animals weight going up is surprising. Lab people surely don't cook meals for the animals and whatever changed in pet food, changed in rat food.

Your lack of surprise is surprising.

Lab animal nutrition is calculated by calories and composition of nutrients, which were determined by controlled and peer reviewed experimentation. There are a number of handbooks on lab animal nutrition available, and here's a slideshow(pdf) with an overview and links to more sources. The effects of feed composition are very well understood, and used to recreate disease models in some animals.

What isn't understood at all is why the same dietary formula from '95 is resulting in heavier animals in 2013. There's science in them thar hills.
posted by Slap*Happy at 6:17 AM on August 9, 2013 [12 favorites]

My other rant is widespread antibiotic use in all sectors of the meat industry and human health.

I'm a calorie-in / calorie-out believer myself but being Canadian and having lived in the UK and now the US I can tell you that chicken is completely different in the United States. There is just so much more visceral fat in American chicken and the meat is way more moist. Unfortunately, it isn't a clear cause of the weight gain because the UK is on a similar weight trajectory and Canada is as well. But it is a weird thing that 'taste like chicken' means something different in different countries.
posted by srboisvert at 7:04 AM on August 9, 2013

Lab animal nutrition is a lot sketchier field than is painted above. A lot of the rodent dietary requirements were based on "Well, we fed this to rats and it didn't kill them. Let's try mice! Oops, mice died; let's reformulate a little." It is not designed for optimum nutrition for mice or rats, that's for sure.

The control data the authors are so excited about for lab rats and mice are from tox studies. Tox studies generally involve outbred mice and rats. Outbred rodents retain some heterozygosity, as opposed to inbred ones, and therefore are subject to selection pressure at the vendor level.

Vendors have large rooms in which the mice and rats are bred. These rooms are staffed with people, not robots, and those people are responsible for selecting the future breeders. There are supposed to be criteria for selecting breeders, but animals that "look good" to the people working in the room are always going to be chosen first. Animals that "look good" are often heavier for their age and put on weight more rapidly. You could maybe even throw some crappy pop psychology in there and say that maybe since people are more used to looking at overweight people and overweight pets, that the bigger animals look more "normal" to them.

Solely by natural breeding, I can make you a rat that is close to a kilo at a year. I could do this in probably a year of concentrated breeding. It is not surprising that outbred animals have gone up in weight over 10 years. What it should tell the lab animal vendors, though, is that it's time to take a look at the animals and adjust the weight charts again.
posted by marmot at 9:11 AM on August 9, 2013 [3 favorites]

Lab animal nutrition is a lot sketchier field than is painted above.

Uhh... not so sure about that. What's more, feed manufacturers precicely document(pdf) what goes into their product. They're not chucking leftover seedcorn into burlap sacks labeled "For Science Critters."

What it should tell the lab animal vendors, though, is that it's time to take a look at the animals and adjust the weight charts again.

Rats, mice, vervet monkeys, chimpanzees... are all subject to vendor selection, and the vendors have been consistently selecting for fatter animals for all lab species? At the same time as wild and domestic animal populations have been increasing in weight?

That's not even close to passing the smell test. It can be easily tested by weighing the animals selected for breeding by the vendors and measuring against the animals they did not, tho, and that should be one of the first follow-on studies.
posted by Slap*Happy at 10:05 AM on August 9, 2013

You aren't really getting scientists throwing cheetos and mcnuggets at animals.

Riiiiiight. Actually, I've seen * real scientists* feeding lab animals some pretty strange things out of their lunch bags when the animals weren't on a stringent feeding protocol....
posted by BlueHorse at 2:27 PM on August 9, 2013

I think that we need a little more granularity here.

Yes, some laboratory mouse populations have their nutritional input monitored and regulated.

Most of the mice and rats we use in my former little subfield of neuroscience were raised ad libitum water and food pellets. Some of the behavioral transgenic mice might have their diet restricted, but mostly so they'll want the 'reward' food pellet or water during studies. Hmm, interesting idea, some behavioural interpretations could be due to differences in satiety which has nothing to do with the primary transgene but somehow the insertion messed up neighbouring genetic elements a bit, but I digress.

There might have been a shift in what lab animals were used for between then and now. 20 years ago there was a lot more routine behavioural studies. Nowadays, a lot more animals are used just for their brains. Well, brain tissue for in vitro culturing or manipulation. Kind of like shifting from primarily working class to a more sedentary office class of employee.
posted by porpoise at 7:01 PM on August 9, 2013 [1 favorite]

Precisely document, you say? Hmmm. It didn't get a lot of mainstream press, but we lost some studies, as did our clients, and had problems with animals. We analyze our diet 4x/year. We do that because we don't take the manufacturer's word for it because it's often incorrect. Have you been to a feed plant? I have.

I own the book cited. Take a look at the references. It hasn't been updated since 1995 (look at the advances in human nutrition, including epigenetics, metabolomics, microbiomics, etc, since then) and the state of feeding lab animals reflects that. Do you know what the feed conversion rate in a mouse is? It's criminal, is what it is. It takes something between 75 and 90 kg of feed to make 1 kg of mice. It takes 1.1 kg of feed to make 1 kg of salmon. That shows us that, well, not only are salmon very efficient feed converters, but that we don't know what the hell we're doing with feeding mice.

If you also look at the health of the rodents (can't speak to the macaques or vervets or chimps), it has increased dramatically since 1995. In 1995, almost every colony everywhere had some sort of Helicobacter, a lot had mouse parvovirus, and quite a few had mouse hepatitis virus as well. It's not as bad as it was in the '60s and '70s, but as the health status of animals has gone up, I would bet their weight has, too.

I'll give you the chimps. The chimps I can't explain, but both macaques and vervets are bred in captivity by humans and might be subject to similar pressures. The wild animals also showed less weight gain over time than lab animals, so the weight gain isn't just due to this mystery factor, whatever it is.
posted by marmot at 8:03 PM on August 9, 2013 [5 favorites]

1) There is a difference between precise and perfect, and you know it.

2) If the science hasn't been updated, and the feed is generally based on it, why has weight increased in captive lab animals when fed the same diet decade over decade? If the quality of feed has increased, how can that be correlated with weight gain? Are there studies that show new formula feed makes for heavier mice? If the population of lab animals are healthier, and show significant weight gain, isn't that an area we should be investigating?

3) Less weight gain is still weight gain.

There is a ton of science in this you are hand-waving away. You've presented some interesting follow-up studies, but your dismissal of the linked study is unconvincing, considering it's based mostly on speculation built on a multi-factored rube-goldberg "perfect storm" scenario.

There is nothing about this study that is unsurprising. There may be no "factor X", but it's going to take more science to figure that out.
posted by Slap*Happy at 8:27 PM on August 9, 2013

I bet you a nickle it'll turn out to be evolution of gut bacteria. Bacteria that secrete something that causes their host to eat more are more successful bacteria. They have more nutrients and can reproduce in larger numbers. I'll bet another nickle that within ten years, Gut-Ecologist will be a legitimate medical specialization.
posted by gregor-e at 5:29 PM on August 10, 2013 [1 favorite]