It's a huckster's dream: "Try the new Burmese Python Diet. No calorie counting or special foods. Eat whatever comes along, up to a quarter of your body weight. Not only is it good for your waistline; it's good for your heart."
Trouble is, what works in pythons probably won't work for humans.
Pythons employ what scientists call a "sit and wait foraging tactic." In other words, they lie around in a jungle and wait for the food to come to them. And of course, this can mean months between meals.
Still, these infrequent but humongous meals are actually normal for the python. A python's heart gets far larger and stronger after it gorges, and scientists are trying to understand how that happens, and whether it can help humans with heart diseases.
Heart growth isn't always a healthy thing. A diseased heart can get larger as well. But like any other muscle, the heart will grow larger and stronger after it gets a prolonged workout.
"Lance Armstrong and Michael Phelps undoubtedly have huge hearts," says University of Colorado biologist Leslie Leinwand. But the growth a human heart is capable of is nothing compared with what a Burmese python can do after it eats a big meal.
"Within two to three days [the snake] can get anywhere between a 30 and 40 percent increase in the mass of the heart," says University of Alabama snake expert Stephen Secor. The growth comes following a meal, because the large meals pythons infrequently eat send their metabolism through the roof and put huge demands on their hearts.
Secor and Leinwand have a paper out in Science Saturday in which they show that it is the ratio of three fatty acids in the blood that prompts the heart growth in snakes. They found that the same ratio of fatty acids injected into a mouse will cause its heart to grow as well.
So why won't eating a large meal cause a human's heart to grow? Part of the answer is the scale of our meals relative to our size.
"Could you swallow a totally intact meal that weighs a quarter of your body mass?" asks Secor. In other words, could you eat a 30- or 40-pound pig in a single sitting? "If you could, I guarantee you your metabolic rate would go through the roof," says Secor.
Of course we're not designed for such meals. But even if we could consume a whole pig we'd have to digest bones, hair and all. And that could cause some major problems — most food we do eat undergoes some amount of processing that makes it possible to eat.
So even though we're all keen on stronger hearts, we'll probably have to leave the Burmese Python Diet to the Burmese python.
SCOTT SIMON, HOST:
This is WEEKEND EDITION from NPR News. I'm Scott Simon.
Running marathons can help you build a healthy heart but there's a simpler way to cardiac fitness, as practiced by pythons. They just eat. A python's heart can rapidly grow by as much as 40 percent simply by devouring a huge meal.
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SIMON: I have a little something in my throat just thinking about it. Now researchers think they've figured out how pythons perform this postprandial feat.
NPR's herpetology correspondent Joe Palca has the report.
JOE PALCA, BYLINE: Talk about sedentary; the Burmese python puts a couch potato to shame. To get a meal, pythons employ what scientists call a Sit and Wait foraging tactic. In other words, they lie around in a Burmese jungle and wait for the food to come to them. Perhaps not surprisingly, this can mean months between meals.
When they do eat, the meal can be huge - a 40 pound pig, for example - and suddenly, these sedentary snakes switch into metabolic high gear.
PROFESSOR STEPHEN SECOR: Imagine running a marathon for five days non-stop. That is what these snakes are experiencing metabolically when they're digesting a meal.
PALCA: Stephen Secor studies snakes at the University of Alabama, Tuscaloosa. He says all this digesting means the python's heart has to step up its game and pump a lot more blood to the snake's digestive system.
SECOR: So it responds like any other muscle that's, you know, experiencing chronic use. It grows.
PALCA: This is the same thing that happens to the hearts of long distance runners but to a much greater degree in the python.
SECOR: Within two to three days, you can get anywhere between a 30 and 40 percent increase in the mass of the heart.
PALCA: As the meal is digested, the heart returns to normal.
Leslie Leinwand became intrigued by the python. She's a molecular biologist at the University of Colorado, and she studies hearts but mostly mammalian hearts. She was a bit intimidated by studying pythons, and then she figured...
PROFESSOR LESLIE LEINWAND: Why not?
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LEINWAND: Let's build a python colony here.
PALCA: With the help and advice of Stephen Secor, she built her colony of pythons and started looking for an explanation about why the heart growth occurs. The first clue came from the python's blood.
LEINWAND: Within 24 hours after feeding, the blood is like milk. There is so much fat in it that you can't see through it. I mean, it's completely opaque.
PALCA: This was obviously good fat, so Leinwand asked her junior colleague Cecilia Riquelme to find out what it was made of.
LEINWAND: Before she did that, though, she took a big leap, and did an experiment that I told her would never work, so she shouldn't bother doing it. And that's the wonderful thing about science - she ignored me and did it anyway.
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PALCA: The experiment was to take blood from a postprandial python and inject it into a mouse. To Leinwand's surprise the mouse heart also increased in size.
LEINWAND: What that means is that it was more than of academic interest to people who study reptiles and pythons.
PALCA: It had implications for healthy heart growth in mammals, possibly even humans. As they report in the journal, Science, Leinwand and her colleagues have now figured out that it's a particular ratio of three fatty acids that hold the key. Simply by injecting the right ratio of these fatty acids into a hungry python, its heart would begin to grow.
Leinwand says she faced some skepticism when she started studying snakes.
LEINWAND: Most of my friends said, why are you doing this? You know, what is a python going to tell you that's relevant to a mammal? And I said just wait and see.
PALCA: Who'd have thought that pythons might hold the key to a healthy heart?
Joe Palca, NPR News, Washington. Transcript provided by NPR, Copyright NPR.