Scientists Calculated How Many Calories Are in a Human, and the Answer Is Surprisingly High

The average human body contains enough edible muscle to provide more than 32,000 calories, and when organs, fat, and other edible tissues are included, that figure climbs to an astonishing 143,771 calories. On paper, those numbers make humans sound like a surprisingly valuable food source, especially during times of famine when every calorie can mean the difference between life and death. Yet despite that nutritional value, nearly every society throughout history has treated cannibalism as one of humanity’s strongest taboos, often viewing it as an act beyond the limits of acceptable behavior.

A new scientific study suggests there may be a very practical explanation for why that taboo became so widespread. While consuming human flesh can provide enough energy to help someone survive under the most desperate circumstances, the long-term biological consequences are so severe that communities practicing cannibalism would eventually face devastating outbreaks of disease. According to the researchers, this hidden cost may have played a major role in shaping one of humanity’s oldest and most universal social rules, helping societies avoid practices that threatened their survival.

Scientists Examined Cannibalism From a Survival Perspective

Cannibalism has appeared repeatedly throughout human history, although almost always under extraordinary circumstances. Archaeologists have uncovered prehistoric human bones bearing the same cut marks found on hunted animals, suggesting that some ancient communities occasionally processed human bodies for food. Historical records also describe isolated cases during famines, shipwrecks, sieges, and survival disasters where desperate people resorted to eating the dead after exhausting every other available food source. While these examples remain rare, they have continued to raise difficult questions for scientists studying human evolution.

Rather than focusing on morality or cultural traditions, the researchers approached the issue as a question of survival. They wanted to understand whether cannibalism could ever offer an evolutionary advantage by treating the human body like any other potential food source. Their model compared the calories that could be gained from eating a person with the energy required to obtain, prepare, and consume the meat, while also accounting for the biological risks involved.

“This coexistence of recurrent practice and persistent prohibition raises a fundamental question: when does cannibalism become adaptive, and why is it typically suppressed?” the researchers wrote in their paper. By examining both the rewards and the costs, they hoped to understand why societies across vastly different cultures arrived at remarkably similar conclusions about avoiding the practice.

Instead of assuming cannibalism was either entirely irrational or occasionally beneficial, the team attempted to quantify every major factor that could influence survival. Their findings revealed that while there are situations where consuming human flesh can provide a short-term advantage, those benefits disappear surprisingly quickly once the broader consequences are taken into account.

How Many Calories Does a Human Body Actually Contain?

To answer their question, the researchers first needed to estimate how much energy the average human body actually provides. They calculated that edible muscle contains approximately 32,376 calories, while including fat, organs, connective tissue, and other edible parts raises the total to around 143,771 calories. Although those figures may seem enormous at first glance, they become far less impressive when compared with many large animals that humans have hunted throughout history.

The researchers estimated that the edible muscle alone could provide roughly 65 portions containing 500 calories each, making it a respectable but hardly extraordinary food source. Large game animals often provide significantly more usable meat without presenting the same biological dangers. When viewed from a purely nutritional perspective, humans fall somewhere in the middle rather than standing out as an especially rewarding source of food.

Lead author Dr. Michał Misiak explained that calories alone never tell the whole story. “We looked at the human body as a potential food source, analyzing both the energy benefits and the hidden costs. From a caloric perspective, a human being turns out to be an average meal, especially considering the difficulty of obtaining one.”

Unlike livestock or wild herbivores, humans are intelligent, highly social, and capable of defending themselves or working together against threats. That means obtaining human meat would generally require far more effort and risk than hunting many other animals that offer similar or even greater nutritional rewards.

Hunting Humans Offers Surprisingly Little Return

The researchers didn’t stop at measuring calories. They also estimated how much energy someone would need to spend obtaining and preparing human flesh before it could actually be eaten. Looking only at the calories stored in the body paints an incomplete picture because every hunting strategy comes with costs that reduce its overall value as a food source.

Their model found that if a person had already died from natural causes, preparing the body for consumption would require approximately 5,691 calories in labor, fuel, and food preparation. Under those extremely unusual circumstances, consuming human flesh could remain energetically worthwhile during severe famine because the calories gained would comfortably exceed those spent preparing the meat.

The situation changes dramatically once hunting becomes necessary. Tracking another person, engaging in conflict, transporting the body, and processing the meat all require significant amounts of energy. By the time those costs are added together, the researchers found that the overall return becomes surprisingly small, leaving hunters with little nutritional advantage over the effort they invested.

That makes cannibalism a remarkably inefficient way to obtain food under normal conditions. Hunting wildlife, raising livestock, fishing, or gathering edible plants generally delivers a far better balance between energy spent and calories gained, without exposing people to the unique biological dangers associated with consuming members of their own species.

Disease, Not Calories, Is The Biggest Problem

Although the calorie calculations produced some unexpected results, the researchers concluded that nutrition is not what ultimately discourages cannibalism. The greatest danger comes from something far less visible: infectious disease. Humans share nearly identical biology, giving many pathogens a much easier route into a new host than they would have when passing between different animal species.

“The key problem lies elsewhere: the risk of infection,” Dr. Misiak explained. “Pathogens have an easier time because they enter a body with an almost identical physiology.” That shared biology allows dangerous viruses, bacteria, parasites, and especially prions, the misfolded proteins responsible for fatal brain disorders, to spread far more efficiently between people.

As the researchers expanded their model, they found that these risks increase rapidly over time. The longer cannibalism continues within a population, the greater the opportunity for deadly diseases to circulate through the community. If people consume individuals who themselves practiced cannibalism, those dangers multiply even further, creating conditions where epidemics could spread with alarming speed.

Rather than providing a reliable survival strategy, widespread cannibalism would gradually weaken entire communities by increasing illness and mortality. According to the researchers, that escalating biological cost eventually outweighs any temporary nutritional benefit, making the practice unsustainable over the long term.

Why Cannibalism Never Became a Sustainable Food Source

As the researchers continued testing different scenarios, one conclusion became increasingly clear. Cannibalism might offer a temporary source of nutrition during periods of extreme starvation, but it quickly becomes a losing strategy once disease begins spreading through a population. Every additional case increases the likelihood that dangerous pathogens will pass from one person to another, gradually turning a desperate survival tactic into a major public health threat.

The model also showed that the risk rises even further if the person being consumed had previously practiced cannibalism themselves. That creates a chain reaction where infections become increasingly common with each generation, making it difficult for communities to avoid widespread illness. Over time, the biological consequences become so severe that any short-term caloric advantage is completely overshadowed by rising mortality and declining population health.

Dr. Michał Misiak believes this may explain why so many different societies independently developed strong cultural prohibitions against eating human flesh. “The taboo acts as an evolutionary safety net,” he explained. “Our results suggest it’s a biologically justified response to the growing risk of epidemics. Societies that didn’t curb cannibalism simply didn’t survive.”

Instead of viewing the taboo as purely moral or religious, the researchers suggest it may also have served a practical evolutionary purpose. Communities that discouraged cannibalism would have been far less likely to experience devastating disease outbreaks, giving them a better chance of surviving and passing those cultural norms to future generations.

The Findings Challenge Long-Held Historical Claims

Beyond explaining why cannibalism remained rare, the study also raises questions about historical claims that certain societies regularly practiced it. Throughout history, accusations of widespread cannibalism have frequently been used to portray rival groups as uncivilized or to justify conquest and violence against them.

European colonizers, for example, often claimed that Indigenous communities in the Americas routinely practiced cannibalism. Historians have long argued that many of these stories were exaggerated or entirely fabricated to support colonial expansion and present Indigenous people as barbaric. The researchers believe their findings add another reason to approach such claims with caution.

According to the team’s model, habitual cannibalism would expose communities to such significant disease risks that maintaining the practice over long periods would be extremely difficult. While isolated incidents during famine or ritual contexts certainly occurred, widespread and continuous cannibalism would likely have produced serious biological consequences that made it unsustainable.

“A central interpretative implication of the model is that cannibalism is inherently high-risk and therefore unlikely to be practiced regularly over long periods,” the researchers wrote. They added that reports describing large populations routinely consuming human flesh, particularly during times when food was otherwise plentiful, should be treated carefully unless supported by strong archaeological or historical evidence.

What the Study Says About Human Survival

Although the topic naturally grabs attention because of its shock value, the researchers stress that their work is really about understanding how humans adapted to survive. By examining the balance between calories gained, energy spent, and disease risk, they were able to explore why certain behaviors disappear while others become deeply rooted in culture.

Their findings suggest that cultural taboos are not always arbitrary traditions. In some cases, they may develop because they help communities avoid behaviors that threaten their long-term survival. Cannibalism appears to be one example where biology and culture may have worked together, reinforcing a practice that protected populations from catastrophic outbreaks of disease.

The study also highlights how evolutionary pressures shape human behavior in ways that are not always obvious. While people often think of survival in terms of finding enough food, avoiding deadly pathogens can be just as important. A practice that appears beneficial in the short term may ultimately become harmful if it increases the spread of fatal illnesses throughout a community.

Researchers hope their model will encourage further investigation into how biological risks have influenced other long-standing social customs. Understanding why certain taboos emerged could provide new insights into the relationship between human evolution, culture, and public health.

Why Chicken Still Wins Every Time

For anyone wondering whether the numbers change humanity’s place on the food chain, the answer is a decisive no. While the human body contains a respectable amount of calories, it offers surprisingly little advantage once the effort of obtaining it and the enormous health risks are taken into account. Other food sources are simply safer, easier to acquire, and far more sustainable over time.

The study paints a picture that is both unsettling and fascinating. Humans may technically be edible, but evolution appears to have stacked the odds heavily against making each other a regular meal. From disease transmission to the energy required for hunting, nearly every factor pushes societies toward finding food elsewhere.

That may explain why one of humanity’s oldest taboos has endured across continents and civilizations for thousands of years. The instinct to avoid cannibalism may have protected countless generations long before anyone understood bacteria, viruses, or prions. Sometimes the oldest social rules survive because they quietly solved problems our ancestors couldn’t yet explain.

Sources:

1. Misiak, M., & Tureček, P. (2026). The cannibalistic trade-off: Why human cannibalism emerges and why taboos suppress it. Proceedings of the National Academy of Sciences, 123(27), e2605120123. https://doi.org/10.1073/pnas.2605120123
2. Misiak, M., & Tureček, P. (2026b). The cannibalistic trade-off: Why human cannibalism emerges and why taboos suppress it. Proceedings of the National Academy of Sciences, 123(27), e2605120123. https://doi.org/10.1073/pnas.2605120123