Apparently, I’ve been living under a rock for the past several years, because this week marks the ninth — count ‘em ninth — year in a row that the brown bears of Alaska’s Katmai National Park will be pitted against each other in an all-out, winner-take-all, single-elimination tournament that draws spectators from around the globe.
And what are these bears fighting over? Territory? Mates? Nope. At stake is a winter’s worth of bragging rights and the title of Fattest Bear of the Year. Here’s how it works:
On October 5, the park published this year’s bracket, showing which bears would go head-to-head for the first round. Fans from all over the then logged into the website to look over the photos of said bears (who are identified by number, though the most popular among them have nicknames like “Otis” and “Fluffy Gams”), and cast their vote for which bear they believe “best exemplifies fatness.” Sort of like the cruel, Zuckerberg-designed “Hot or Not” game that would eventually become one of America’s largest and most evil corporations… but with a fun, eco-bent.
According to Explore.org, Fat Bear Week is a body-positive “celebration of abundance and fat bear butts,” and it has flooded my instagram feed with some of the most fun posts I’ve seen in a long time:
Lest we begin canceling the National Parks Service for fat-shaming, you should know that “Winter arrives quickly in Katmai and bears must get fat to survive it. In the bear world, fat exemplifies success. It is the fuel that powers their ability to endure winter hibernation as well as the key to their reproductive success.”
The mystery of hibernation is one that scientists are only starting to unravel. The bears grow “profoundly insulin resistant” over the winter, yet remain perfectly healthy — quite a trick. How do they do it? An article in last week’s Washington Post quoted a 2019 study showing that “more than 10,000 genes in bears that work differently during hibernation vs. in autumn or spring.” Another study, published just this past month, compared blood samples from bears throughout the year, and found that eight proteins differed substantially from one season to the next.
from bears to squirrels
So the answer is… it’s complicated. A few weeks ago, I quoted a passage from Gary Taubes’s book Why We Get Fat. It involved the fact that like fat bears, acorn-loving squirrels double their body weight during late summer in preparation for winter hibernation.
But I have to admit that I didn’t give the whole picture. The passage is from a chapter of the book called “The Laws of Adiposity,” which questions the conventional wisdom that weight gain is a result of eating too much. Rather, Taubes asks, what if it’s the other way around?
“But these squirrels will accumulate this fat regardless of how much they eat… They can be housed in a laboratory and kept to a strict diet from springtime, when they awake from hibernation, through late summer and they’ll get just as fat as squirrels allowed to eat to their heart’s content.”
Having a big stockpile of fat is essential to the squirrel’s survival during the winter — so much so, that Mother Nature sees to it the squirrel will fatten up in the fall, even if it is underfed.
This certainly doesn’t square with our traditional model of weight gain, which says that we eat food, burn as many calories as we need, and store the rest. If we’re storing too much, it means that we’re eating too much. The squirrel model, on the other hand, says that mother nature determines how much we will store — before we ever take a bite. How could this be?
Taubes believes that the key is hormones. More of the animal’s calories are driven into fat storage, because that’s where they need to be. Fewer are burned for energy, sacrificed to the more important survival mechanism.
from squirrels to humans
Taubes believes that for squirrels in nature — for all animals, in fact — adiposity (aka, chonkiness) is “carefully regulated, if not exquisitely so,” using Mother Nature’s go-to tool: hormones. Hormones regulate everything necessary for our survival, from our reproduction, to our body temperature to our blood pressure to our immune function. Logically, then, it’s hard to believe hormones would not be involved in something as important as how we fuel our bodies.
Meanwhile, it’s pretty well-known that our hormones fluctuate throughout the day: cortisol is highest in the morning, melatonin at night. These changes are part of what’s called our “circadian rhythm.” “Circa,” means “around” and “dia,” means “day.” Thus, these changes happen around the same time each day.
Well, a 2013 paper in Frontiers in Neuroscience looked at what the researchers called “circannual” changes in hormones in humans. The researchers noted that:
“A number of neuroendocrine pathways, two of which are the endocrine mechanisms underlying feeding and stress, appear to show seasonal changes in both their circulating levels and reactivity. As such, variation in the level or reactivity to these hormones may be crucial factors in the control of seasonal variations in food-seeking behaviors.”
In other words, it may well be that, like Otis and his friends, we humans experience certain changes in our blood chemistry that influence our eating behaviors and our stress levels at different times of year.
The jury’s still out on much of this, but it does offer some interesting possibilities. Scientists are studying those bear-blood proteins for possible pharmaceutical application in treating diabetes in humans. Meanwhile, if we accept that hormones play a role in the development of weight gain — which they almost assuredly do — then maybe we can ease up on the fat-shaming when we find ourselves putting on a bit of extra “fluff” for the winter. It could very well be the season itself that’s to blame, and not just the pumpkin pie that comes with it.