Almost everyone in today’s world is obsessed with managing their weight; usually with trying to keep
it off. The Freshman 15, post-pregnancy weight gain, quarantine 15, the beer belly that won’t
go away after a certain age...almost all of us are on the lookout for these extra pounds and
trying to find ways to avoid them. Wouldn’t it be great if we could just eat whatever we wanted and
never get fat instead? Well, if you were a beetle or a cockroach, that’s exactly what would happen.
The rest of your short life scurrying through sewers or frightening new tenants and leading
to subsequent fights with landlords would probably be pretty terrible, but you wouldn’t be fat! So we
wanted to answer a question most people hadn’t even thought of: why can’t insects get fat?
Let’s start by clarifying that this doesn’t necessarily apply to all insects. After all,
there is a whole, wide, terrifying world out there with over 900,000 different kinds of living
breeds of insects on our planet. This represents around 80% of the world’s total number of species.
So while most of them can’t get fat, at least in the way we imagine “fat” to look and be, a
few can. For example, overweight dragonflies have been found in the wild, and the extra weight seems
to have the same negative health effects it has on humans. Namely, reduced mobility and lifespan.
One scientist also overfed mosquitoes using a hand dropper to see if they would gain weight.
No, we don’t know who funded this study. By feeding mosquitoes the right combination of foods,
scientists realized they could convert half of mosquitoes’ bodies into fat.
As this probably decreases their ability to fly around spreading disease, sucking peoples’ blood,
and ruining summer barbecues for everyone, no one really minds fat mosquitoes.
However, other species, like academia’s favorite bug to study and torment - the
fruit fly - don’t actually expand in size when they’re fed extra calories.
Don’t get us wrong, fruit flies who take in excess
food will store it as excess lipid droplets in their cells.
But why don’t those lipid droplets show up as a little fly tummy or chubby fly thighs?
Well, mature fruit flies have a hard, chitin exoskeleton. Meaning that no matter how much
“fat”, a.k.a. lipid droplets they gain, their bellies will never expand because
they can’t stretch out the exoskeleton. The fat simply ends up getting packed in tighter.
While fat ends up as fat tissue in human bodies, fat in fruit flies - and plenty of
other insects - ends up in a unique insect organ called the “fat body”,
which among performing many other tasks, also functions as the insect’s liver. This isn’t
a contained, separate organ, but rather, is situated throughout the insect’s whole body.
The fat body will push against the exoskeleton from all sides, but it will never actually be
able to expand it, as adult insects don’t shed their exoskeleton as babies do. It still sounds
extremely uncomfortable, like trying to fit back into your high school prom dress at 35.
Though too much fat stored in this organ creates a problem, too little at can as well.
The fat body is great at detecting and using nutrient reserves; that means that it uses
its inventory of stored nutrients to determine everything from insect growth and reproduction
to when the appropriate time is for metamorphosis. If the insects aren't
getting enough [emphasis] fat, growth and metamorphosis will be delayed or stunted.
However, the fact that extra fat can’t be seen in most insects doesn’t mean it’s not causing damage.
Fruit flies who regularly overeat and increase the fat in their bodies develop
something similar to diabetes, and tend to die younger than their average-sized
friends. Keep in mind that a fruit fly’s usual lifespan is about 30 days,
so dying even a few days’ earlier is actually kind of a big deal.
What does all this mean for humans though? After all,
growing an exoskeleton to prevent ourselves from gaining weight seems...challenging.
And clearly, cutting down on soda and Taco Bell is out of the question.
Are there other ways insects avoid getting fat that we could mimic instead?
Actually, there are plenty! Which brings us to one
of the most ubiquitous and friendly insects around: the friendly, hardworking old ant.
Ants are easily able to take on extra calories; however,
they don’t keep them for long. Being the classically communist little workers they are,
they feel obliged to share them with the rest of their nest.
You see, ants have two different types of “stomachs”. One is the midgut,
the ant’s digestive stomach, which the ant uses to stock up on its own food and obtain
its energy. The other is the social stomach or crop.
This is an entirely separate food-storage organ than the ant’s regular stomach.
When the ant has filled up her caloric needs in her midgut - all worker and soldier ants
are female, so “her” is accurate - the rest of the calories go to the crop. If the ant gets
hungry later and hasn’t yet emptied her crop, some of that food might move to the midgut.
However, it’s more common for the food to be passed onto a fellow hangry worker ant.
A hungry ant will use her antennae to tap the overfed ant using a special code.
This signals the overfed ant to feed her workmate. At which point, the overfed
ant…[pause]...vomits up the food so the hungry ant can get it.
Yeah, turns out there’s no pretty way to pass food on from one organism’s stomach
to another’s mouth. It’s exactly as gross as you were thinking.
At this point you might be wondering, why should we even care if insects can get fat or not?
What difference does it make for us? Is there a juice cleanse or a keto
diet plan we are testing on insects that can work on humans as well?
First of all, no there isn’t, mostly because juice cleanses are BS.
Second of all, some of the observations about fat in insects are helping scientists understand
the role of diet and genetics in human obesity, which is currently a rapidly-spreading epidemic.
Caterpillars are one of the species used to test the role of carbohydrates
and proteins in fat accumulation. To the average human, the round,
squishy body of a caterpillar may already look fat, but that’s actually just the caterpillars
acquiring the nutrient storage they need to eventually turn into a stunning butterfly.
In reality, it’s pretty hard to make a caterpillar fat. Scientists - and we
continue to be confused as to who exactly is funding these studies - fed two groups
of caterpillars radically different diets. One was low in carbs and high in protein,
and the other diet was high in carbs and low in protein.
Researchers found that over several generations, around eight to be exact,
caterpillars used to a high-carb diet developed the ability to eat all the carbs they wanted
without gaining extra weight. Whereas caterpillars used to a low-carb diet
stored almost all carbs as fat, to protect their health and body.
This might go some way towards explaining why carbohydrates are generally considered
a poor food choice for humans looking to lose weight. High-carb diets are a fairly
recent development in human evolution, as they only came about after the advent
of agriculture. Our cavemen ancestors’ diet was much more protein and fat heavy.
Since we consider humans to be a tiny bit more complex than caterpillars,
it would logically take way more generations for humans to adapt to this carb-intensive diet
that is radically different than that of Stone Age humans. So no matter how long we
feel like we’ve been scarfing down bread, rice, French fries, and delicious pasta,
all these foods are still a relatively new experience for the human race.
Insects aficionados have also found genetic links to obesity in insects that are shared by humans.
In the 1960s, entomologist Winifred Doane found a really fat group of flies in Nigeria.
We don’t even want to think about the amount of time one must spend looking at flies to
automatically clock one buzzing by you as obese, but Doane was apparently on top of her fly game.
When she examined the critters closely, she found they were deficient in the WTDC1
protein. This protein turns off the path that leads to excess fat accumulation.
Therefore, the flies that didn’t have it simply could not stop putting on the pounds.
Or more likely, since they were flies, micrograms.
The interesting part of this finding is that humans have a
gene that controls WTDC1 protein levels as well. And it turns out,
low levels of this protein are linked to problems with weight gain in people.
So we’ve covered two of the three big factors related to human weight, in insects:
diet and genetics. What about exercise? Do insects even lift,
bro? Turns out, most insects can put any gym rat to shame.
You might have heard that ants are able to lift many times their own weight. You might not know
exactly how much more though; turns out ants can carry up to 50 times their own body weight!
To get an idea of how impressive this is, magine a 200-pound human
weightlifter benching 10,000 pounds, a.k.a. approximately the weight of a small elephant!
And ants aren’t even the strongest insects around. That honor goes to the dung beetle,
which really needs to work on its branding.
Dung beetles are able to lift 1,141 times their own body weight. Yes, you heard that correctly.
Remember our elephant-lifting bro from before? Well, if he had a dung beetle’s strength,
he would now be lifting a blue whale - the LARGEST [emphasis] animal on earth.
However, does lifting these crazy weights actually help consume that much energy for insects?
There is evidence to suggest so, as insects that are relatively immobile and don’t carry
weights seem to bloat up. This is especially obvious when it comes to certain honeypot
ants called “repletes”, who almost never leave the nest.
These ants eat a huge amount of food and hardly ever lift or move anything,
thus basically becoming giant balls of sugary nectar. Their only job is to eat as much as
possible, and give all the leftover energy to the rest of the ants in the colony who need it.
Just in case you needed a reminder of how that particular process works,
the calories are transferred by throwing them up. You’re welcome.
In addition to lifting superhuman, superinsect? - loads, many insects
have to expend an incredible amount of energy to do something humans can’t: fly.
When people fly, they sit almost motionless for several hours while snacking on soda and
cookies and crying at “Coco”, thus expending very little actual energy. When insects fly,
they have to increase their metabolic energy by a factor of 50 to 100 just to stay in the air.
For long-term fliers, like mosquitoes and locusts, the fat body circulates a substance called
trehalose, as well as lipids, to help keep the insects in flight. All this activity means that
energy stores are burned up pretty constantly for insects; way more easily than in humans.
In a nutshell, most insects are incapable of getting fat, either because they share excess
calories with their insect communities or burn them up during constant flight and load-bearing
activities. And the insects that are [emphasis] capable of gaining weight don’t usually show it
thanks to their exoskeleton, which basically functions like the tightest corset ever.
Now that you know why most insects aren’t fat, and are still wondering if it’s harder
to create your own exoskeleton or swear off KFC, check out this video, or another video
right here to learn more incredible facts from the team at The Infographics Show!