Holiday weight gain: It’s a real thing in this season of bread stuffing and pumpkin pie.
Many of us haven’t yet looked up from the pantry or holiday table to consider what all those extra calories can do to our waistlines. But one group of creatures at the Duke Lemur Center has been overindulging and plumping up for weeks already, and they’re not the least bit guilty about it.
Since August, the center’s 42 fat-tailed dwarf lemurs have been busy gorging themselves to pack on the pounds they need to survive their winter hibernation.
These squirrel-sized primates are our closest genetic relatives known to hibernate for extended periods of time. By studying how they withstand months of inactivity and yo-yo weight gain with no ill effects, researchers hope to find lessons for humans dealing with prolonged bed rest, diabetes and other challenges to metabolic health.
Some of us carry extra weight in our thighs. Others stash the stuff in a muffin top or a beer belly. As its name suggests, the fat-tailed dwarf lemur stores surplus fat in its sausage-like tail. After two months of feasting, a healthy dwarf lemur’s well-padded appendage can blimp out to 40% of its body weight.
Every week, Duke Lemur Center scientists have been monitoring the lemurs’ girth and watching the numbers creep up on the scale. Now the lemurs are the heaviest they’ve been all year. Nine-year-old Francolin is this year’s champion, having layered on enough fat to boost his weight by some 60% and double the chub in his tail.
All this weight gain is a good thing, says research scientist Marina Blanco, who leads the project. It’s a matter of survival in their native habitat of Madagascar, where their fat reserves help sustain them through the leanest months of the year.
Soon, the animals will curl up and enter a state of suspended animation, dropping their heart rate from 180 beats per minute to as few as eight in order to stretch their onboard fuel for the months-long food coma ahead.
But for now, the lemurs still have business to attend to: breakfast.
On a crisp November morning, they smack and slurp as they wolf down what’s in their bowls: sweet bits of melons, peaches and nectarines, sprinkled with dried cranberries.
Nine-year-old Kiwi is the first to scurry to the food, followed by her daughter, Starling.
“As usual, Jaeger the dad is the last one to get up,” says researcher Lydia Greene.
Their breakfast menu is part of a new project: to steer them towards a more ‘natural’ seasonal diet. The idea is to see if the researchers can make the physiological swings and cycles these lemurs experience in captivity closer to what their counterparts experience in the wild.
Blanco has been ferreting out their wild counterparts in slumber chambers in Madagascar for years to understand how they pull it off.
While we might gain weight overdosing on cookies and eggnog, dwarf lemurs get fat on fruit. Wild dwarf lemurs fill up on persimmons, Grewia berries, and other sugar-rich fruits during the rainy season, in preparation for the subsequent dry season when such foods are in short supply.
It’s not possible to feed North Carolina’s lemurs exactly what they would eat in the tropical forests of Madagascar, so the researchers come up with alternatives that come close in terms of nutritional content.
A typical menu at the Duke Lemur Center might include 12 grams of fruits and veggies, 6 grams of monkey biscuits and a couple of mealworms. But their fall fattening diets follow a different recipe: half the protein, and twice as much sugar in the form of finely chopped pears, figs, kiwi, mangos, papayas. Topped with dried apricots, raisins, dates and the occasional drizzle of honey, this bounty is delivered each morning and midday by their keepers.
“I feel like that's the only time I cook, basically -- preparing the food for the lemurs,” Blanco said.
Both diets contain the same number of calories. But they’ve found that dwarf lemurs fattened on a diet high in sugary fruit prior to hibernation followed more natural patterns of weight ups and downs, building up and then burning through their tail fat more like their wild peers. Their fat tissue was also more similar to the wild lemurs in composition.
Most of us want to get off the weight roller coaster. But for dwarf lemurs, such seasonal swings are the norm.
“I love the fattening. It’s one of my favorite times of year,” Greene says.
The findings were published this summer in the journal Proceedings of the Royal Society B.
CITATION: "Of Fruits and Fats: High-Sugar Diets Restore Fatty Acid Profiles in the White Adipose Tissue of Captive Dwarf Lemurs," M. B. Blanco, L. K. Greene, L. N. Ellsaesser, B. Schopler, M. Davison, C. Ostrowski, P. H. Klopfer, J. Fietz and E. E. Ehmke. Proceedings of the Royal Society B, June 15, 2022. DOI: 10.1098/rspb.2022.0598
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