A new study explores how the extreme biology of pythons may point to an unexpected path for obesity research.
Pythons don’t nibble. They chomp, squeeze, and swallow their prey whole in a meal that can approach 100% of their body weight. But even as they slither stealthily around the forest, months or even a year may pass between massive mouthfuls. That cycle of bingeing and long fasting pushes their metabolism to extremes far beyond anything people experience in daily life.
Researchers at Stanford Medicine and the University of Colorado, Boulder, have now identified a metabolite that surges 1,000-fold in pythons after a large meal. When given to obese lab mice, it caused them to avoid their food pellets and lose weight, producing an effect similar to semaglutide drugs such as Ozempic and Wegovy.
It is still far too early to know whether this metabolite, known as pTOS, could lead to a new weight loss treatment for humans. Even so, the findings highlight the value of studying animals with unusual biology. Reptiles have already helped inspire important medicines for people. Snake venom contains biologically active compounds that have been turned into blood pressure drugs and anticoagulants. Semaglutide itself traces back to the discovery of a hormone in the Gila monster that helps regulate blood sugar.
“Mammals have a relatively narrow physiologic and metabolic range,” said Jonathan Long, PhD, associate professor of pathology and a member of the Wu Tsai Neurosciences Institute. “Humans, for example, eat around 1% to 2% of their body weight each meal, and we eat about three times a day,” unlike snakes, who eat rarely and whose physiology changes drastically after a meal. “Obviously, we are not snakes. But maybe by studying these animals we can identify molecules or metabolic pathways that also affect human metabolism.”
Long is the senior author of the study, which was recently published in Nature Metabolism. Postdoctoral scholar Shuke Xiao, PhD; Mengjie Wang, MD, PhD, a postdoctoral scholar at the University of South Florida; and Thomas Martin, PhD, a postdoctoral scholar at the University of Colorado, Boulder, are the lead authors of the research.
Not exactly lab mice
Pythons are about as far from standard laboratory animals as it gets. They can weigh up to 200 pounds (91 kilograms) and live more than 20 years in the wild. What makes them especially compelling to researchers is how dramatically their bodies react after feeding. Within hours of a big meal, organs including the heart can enlarge by 50% or more. Energy demands jump by more than 40%. Even pancreatic beta cells, which produce insulin and normally do not divide much, rapidly increase in number.
Researchers at the University of Colorado, Boulder, were originally studying that sudden heart growth when they came across pTOS. They collected blood from young Burmese pythons weighing about 3.3 to 5.5 pounds (1.5 to 2.5 kilograms) before and after meals equal to roughly 25% of body weight. In the wild, Burmese pythons can go 12 to 18 months without eating, though the snakes in the lab had fasted for 28 days before feeding. The team also ran similar tests in ball pythons, a smaller relative of the Burmese python.
The blood samples revealed a huge metabolic upheaval. More than 200 metabolites rose at least 32-fold after feeding, while 24 dropped by the same amount. One molecule stood out immediately because it increased more than 1,000-fold. That molecule was pTOS, a little-studied metabolite in humans that is mostly known as a compound excreted in urine.
“We wondered whether this metabolite affected any of the post-feeding physiological changes in the snake,” Long said. “But when we administered pTOS to laboratory mice at levels similar to what we saw in the pythons after eating, we didn’t see any effect on energy expenditure, beta cell proliferation or organ size. What it did regulate was the appetite and feeding behaviors of the mice.”
The researchers found that obese mice given pTOS ate significantly less than control mice and, after 28 days, had lost 9% of their body weight when compared with control animals. The newly svelte mice showed no changes in water intake, energy expenditure or movement throughout the treatment. Additional experiments showed that the effect of pTOS is not due to changes in hormones known to regulate feeding or to a reduction in the rate of stomach emptying, which is one way common GLP-1 medications like Ozempic reduce appetite.
Further experiments determined that pTOS is a byproduct of the breakdown of tyrosine — an amino acid present in dietary protein — by bacteria in the gut. Treating the pythons with antibiotics prior to feeding abolished the eating-associated increase in pTOS levels.
“We were able to work out a pathway in which pTOS is produced after a meal through the metabolism of tyrosine in the gut and the liver,” Long said. “We also found that it then goes to a region of the brain called the hypothalamus, which is a well-known regulator of energy homeostasis. There it activates neurons involved in regulating feeding behaviors.”
The metabolite in humans
The researchers then studied six publicly available datasets of blood from healthy volunteers before and after a meal. In five of the six, pTOS levels were elevated after eating, but only by about two- to fivefold. Such a small increase in humans would be extremely difficult to pick out among many other feeding-associated metabolic changes — illustrating the value of using pythons as a model animal.
But a few people were more snakelike than others. One individual in the databases experienced a more than 25-fold increase in pTOS after a meal, reaching python-level concentrations in their blood. (Because these datasets were from previously conducted studies, it is not possible to know whether this person felt more full or ate less than other study participants.)
Although more research needs to be conducted into the possible use of pTOS in humans to curb appetite, the pythons gave the researchers a plethora of additional molecules to study.
“We’re generating a landscape of molecules that vary in prevalence after eating in all organs of these snakes,” Long said. “We already found many that look like hormones but that have no similarity with any known hormones in mice or humans. This is a form of natural product discovery.”
Long and his colleagues speculate that, like blood pressure medications and anticoagulants, some of these molecules could be clinically useful. “Maybe a patient with Type 1 diabetes due to defective beta cell function could benefit from a snake molecule that stimulates cell division, or a person with liver disease could take a snake-derived drug that facilitates organ remodeling,” Long said.
He noted that there’s an interest among scientists in augmenting human capabilities, such as creating vaccines that enhance the immune response. “Maybe this concept of using molecules first identified in snakes or other animals can extend to many other aspects of human health,” he said.
“We’re excited to learn from these snakes and other ‘extreme’ animals to inspire future discoveries,” he added.
Reference: “Python metabolomics uncovers a conserved postprandial metabolite and gut–brain feeding pathway” by Shuke Xiao, Mengjie Wang, Thomas G. Martin, Barry Scott, Xing Fang, Xinming Liu, Yongjie Yang, Sipei Fu, Steven D. Truong, Jack F. Gugel, Gregory L. Maas, Marcus P. Mullen, Jennifer Hampton Hill, Veronica L. Li, Andrew L. Markhard, Mingming Zhao, Wei Qi, Saranya C. Reghupaty, Meng Zhao, Jan Spaas, Wei Wei, Trine Moholdt, John A. Hawley, Christian T. Voldstedlund, Erik A. Richter, Xiaoke Chen, Katrin J. Svensson, Daniel Bernstein, Leslie A. Leinwand, Yong Xu and Jonathan Z. Long, 19 March 2026, Nature Metabolism.
DOI: 10.1038/s42255-026-01485-0
The study was funded by the National Institutes of Health (grants R01GM029090, R01DK138518, R01DK105203, R01DK124265, K99DK141966, K99AR081618, F32HD112123, F32HL170637, F32DK138685 and T32GM142607), the Wu Tsai Human Performance Alliance, the Stanford Diabetes Research Center, the Phil and Penny Knight Initiative for Brain Resilience at the Wu Tsai Neurosciences Institute, the Ono Pharma Foundation, the Leducq Foundation, the American Heart Association, and the Stanford University Medical Scientist Training Program.
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