Commercially raised chickens are getting (a lot) bigger.

Chicken is the most commonly eaten animal in this country, surpassing beef or pork. And with dietary recommendations that Americans eat less red meat, the obsession with chicken—which has lasted more than 30 years already—shows no sign of stopping.

Maintaining that appetite, though, is already pushing the bounds of what's biologically possible—and perhaps what's humane.

To get a sense of how many more chickens Americans are eating compared to before, take a look at the chart below. The average American eats more than four times as much chicken today as he or she did in the early 1900s, according to data from the USDA. Currently, that amounts to more than 80 pounds per year.

Our collective appetite for chicken isn't sustainable—not given how much of the protein we demand today, and, much less, the amount we're slated to gobble up down the road. And chickens—their genetic makeup, anyway—will likely be forced to adjust.

"If people keep eating more and more chicken, chickens will probably have to get even bigger," said Dr. Michael Lilburn, a professor at Ohio State University's Poultry Research Center. "We' ll have to increase the proportion of breast meat in each bird, too."

Lilburn's estimations are hardly revolutionary. Chickens, after all, have been getting bigger—and breastier—for decades on the heels of inflated demand.

That's because Americans mostly want white meat, so much of it, in fact, that we have long had to export all the extra dark meat that's left over.

And the poultry industry has had to adjust to keep up.

New technologies in the 1940s, which allowed for better nutrition and disease control, as well as improved production management, helped the industry produce broiler chickens more efficiently. Later, advancements in both packaging and transportation further facilitated the growth of commercial poultry companies.

But largely the industry has made do by selecting for certain economically advantageous genetic traits. Specifically bigger birds with bigger white-meat-filled breasts.

A study published last fall chronicled the troubling changes seen in broiler chickens over the past 60 years. Birds, which once weighed just over 900 grams (or roughly 2 pounds) when full grown, now weigh more than 9 pounds. The graphic below, which is based on a graphic created by the study's authors, shows the relative weight of three different breeds. The first was the most commonly used in the 1950s; the second, the most commonly used in the 1970s; and the third is the most commonly used today.


And over-sized breasts are practically an industry standard.

"Now everything is white meat," Lilburn said. "And that's forced the industry to shift toward birds with proportionally larger breasts."

Lilburn doesn't go so far as to lament the state of commercial poultry production. But he does point outthat while many people are quick to complain about industry practices, like the selection of larger birds, they're still eating chicken nuggets, chicken sandwiches, and all sorts of other cheap poultry products.

It would be one thing if people stopped eating commercially produced chicken altogether to protest industry practices, which could force the industry to adjust by selling fewer, lighter and smaller-chested chickens. But that's not happening. In fact, the industry is getting the opposite signal from consumers: to keep making chickens bigger.

"What people don't realize is that it's consumer demand that's forcing the industry to adjust," Lilburn said. "It's a deceivingly small but vocal minority that are raising a lot of legitimate questions. The bulk of the U.S. population still doesn't care where their food comes from, as long as its cheap."

And chicken is cheap. It's easily the cheapest source of protein among meats, and it appears to be widening the gap. For that very reason, Tyson, the largest poultry producer in the country, has predicted steady growth in demand for chicken.

If all goes according to Tyson's plan, poultry physiques are likely to grow even more strange. Chickens, despite appearances, still likely haven't reached their maximum weight limit. And farmers will push those boundaries if America's appetite asks them to.

"I don't think we've seen the limit," Lilburn said. "We'll probably see a limit when we start getting into product quality issues, when the side-effects are too burdensome. But we aren't there yet."