Obesity In Bears: Vital and Beautiful
She was so obese that, from behind, her gait looked more like a waddle than a walk. You could see the fat on her massive butt roll from side to side with each deliberate step. Her dark hair glistened in the fall sunlight.
No, she was not a human with a weight problem. She was a grizzly bear. At 400 plus pounds of jiggling fat and raw muscle, she was stunningly beautiful.
It hasn’t been easy to gain all that fat. Amazingly, she consumed roughly 30,500 kcal of digestible energy every day this fall (link), compared to the approximate 2,700 kcal that a 200-pound couch potato human would need to survive. In Yellowstone, the best foods are, of course, the fattiest, including the seeds of whitebark pine (now scarce due to an unprecedented climate-driven outbreak of mountain pine beetles), army cutworm moths, bison that died from injuries during the rut, or summer-fattened elk (now declining throughout the Greater Yellowstone for a variety of reasons, including climate change.)
Soon, a female grizzly will be as ready as she can be for the slings and arrows of a brutal Yellowstone winter. Starting in a week or more, she will dig herself a den in the earth and simply snooze through the next four to five months of storms, bitter cold and howling winds, powered by her blubber.
Why Fat Matters
For a human, obesity poses serious health problems such as diabetes, but for bears it is necessary for survival. Ample fat is, in fact, the only way that bears can make it through the winter, when they don’t eat or drink or excrete waste for between 100 and 180 days.
How fat fuels the bear’s metabolism during hibernation is nothing short of a miracle. Metabolizing fat produces water, which keeps the bear hydrated even though it is not taking in any water. And, rather than excreting wastes such as uric acid, the bear has unique microbes in its gut that, during the winter months, enables its kidneys to convert urea to nitrogen to make new amino acids, which are the building blocks of protein. With that, bears are able to maintain lean body tissue in the comfort of their own dens without eating or eliminating waste (link). Amazing or what?
Importantly, unlike humans, obese bears do not get Type 2 diabetes. Diabetes occurs when cells lose their ability to take up sugar in response to infusions of insulin. When humans who are starving or who have uncontrolled diabetes rely on fat for energy, the body cannot handle the toxic byproducts of fat catabolism. Not so for bears. Amazingly, they are able to recycle these byproducts into making more fat (link).
For female grizzlies, being obese is especially critical. The fatter a female is at denning time, the more likely she is to birth larger litters of cubs in late January – perhaps three cubs instead of one. And, larger litters are especially important if populations are threatened as in the lower 48 states. Since cub mortality can be as high as 60% or more, producing larger litters is vital to recovering imperiled populations.
If a female grizzly is too thin when she enters the den, her body will not produce cubs. While bears breed in early summer, the small embryo or blastocyst of a pregnant female floats around in the uterus for months. In fact, the amount of body fat accumulated by a pregnant female determines whether the blastocyst implants in the uterus--or not--once she dens. If she is in poor condition, the embryo is reabsorbed. If she is in good condition, it implants.
This strategy makes sense, given that the birthing process entails a major physical commitment by the prospective mother. Being thin could kill her and her cubs.
Part of the challenge facing mother grizzlies is that their cubs are so small and helpless at birth. In fact, grizzly bear cubs are the smallest of any terrestrial mammal in comparison to their grown size – which is one reason why they need to stay in a protected den, until they are big and strong enough to survive when they emerge with their mom in the spring. Proportionally, bear cubs are one tenth the size of a human infant at birth.
To grow a cub quickly, a mother grizzly produces some of the richest milk of any known land mammal. With such nourishment, a cub’s body weight will have increased 12-20 times by the time it follows mom out of the den to greet the wilderness. How does the mother produce such high-quality milk while not eating or drinking? Again, from her own fat accumulated last fall.
Mining the Adaptations of Bears to Benefit Humans
Medical researchers have long been fascinated by the adaptations of bears to the challenges of hibernation. They see potential benefits for people with diabetes and a host of other problems such as heart disease, osteoporosis, as well as traumatic injuries (link). (If you could induce hibernation in someone with a stroke or undergoing cardiac arrest, you could buy doctors precious treatment time).
Interest among medical researchers in obesity among bears is increasing. Just two weeks ago, a new study of captive grizzlies was published showing that a diet high in saturated fats had no adverse consequences on the study animals, at least in the short term (link). The involved bears were fed the equivalent of 84 Big Macs per day, or roughly 6 Big Macs per day if the study had been of average-sized people.
Researchers have a long way to go to solve the mysteries of hibernation, especially if they want to derive practical benefits for people. However, they are making some progress. For example, they have found that bears produce a parathyroid hormone which maintains bone density and strength, and offsets deterioration that would occur while snoozing for so long. But it will be a while before doctors know enough to be able to use this hormone to treat humans suffering from osteoporosis.
Scientists are even further away from applying insights into bears’ adaptations to obesity. For now, we are faced with the grim reality that being obese puts we humans at greater risk of diabetes, heart disease and some types of cancer.
Equally problematic is the fact that in today’s fat-phobic, fat-hating culture, overweight women are especially stigmatized. Author Roxane Gay explores the complexities and paradoxes of her relationship with her body and with being fat in a fascinating new memoir Hunger: A Memoir of (My) Body. In particular, she examines the self-destructive tendencies perpetuated by a male-dominated society that still demands that women be invisible and passive.
Perhaps the esteem in which ancient peoples held corpulent bears would be instructive for modern humans, especially for women in cultures struggling to find a different, healthier and more respectful understanding of what it means to be fat.
Fat in Bears and Humans in Prehistoric Times
Our prehistoric ancestors clearly had a different relationship with fat. The oldest known sculptures, found across Europe and Eurasia into the deeps of Siberia, were of obese women. In fact, “Venus” figurines, which are believed to symbolize fertility, have been dated from 11,000 to as old as possibly 30,000 years.
Similarly, this region boasts the oldest known paintings of bears, which waddle across cave walls with exaggerated rotundity. Paintings of portly cave bears in Chauvet in southern France have recently been dated as far back as 35,000 years ago:
Fat in people and bears has long been seen as a sign of health and reproductive fitness, even unto the Rubenesque curves of idealized Early Modern women. Being thin meant few reserves for surviving the inevitable hard times.
Towards A Different Relationship with Fat
The relationship between ancient cultures and bears has always been one of respect and reverence. Anywhere bears live, stories have long been told about people turning into bears, bears turning into people, and people marrying bears. To native peoples, bears are seen as relatives, teachers, healers, and guides.
Thus, at its root, being fat is seen as being bear, and, in some ways, as being a superior human.
These ancient relationships are fueling mounting opposition by First Nations and Native Americans to trophy hunting grizzlies in Canada and the US. To our First Peoples, trophy hunting is an anathema. It is the ultimate objectification of a kindred animal -- not unlike the problematic objectification of women.
The point here is that native peoples have long held sacred an animal that has to get obese to survive. In these cultures, fat is often appreciated as essential, even beautiful.
Moreover, the bear, with its ability to seemingly die in winter and remerge in spring with new life, has long symbolized transformation. Long before we had the story of Christ, humans told the story of bears and their annual resurrection – a story that relies on the protagonist being fat.
Perhaps the grizzly bear, with its miraculous and long-revered adaptation to obesity, can help us move beyond Hollywood’s stultifying, objectifying female stereotypes, towards a different understanding of what it means to be fat—and human.
We can start by reminding ourselves that recovery of grizzlies in the Heart of the Grizzly Bear Nation (link) —in places such as Yellowstone, Glacier, Waterton and Banff—relies on obese females. Males don’t matter so much (sorry guys), but fat, successful mommas do.