Understandably, that spurred all sorts of reactions: Vegetarians answered with smuggery, omnivores with scorn, and the meat industry responded with a defiant "that's not true!"
But now that the initial shock has dissipated— now that people are bringing the study up less and less at dinner — what remains to be seen is if the news will carry any kind of lasting effect. Will Americans, having heard that their love of pork belly might cause a little more than a few extra pant sizes, change their breakfast orders? Or will everyone simply continue eating as they had been, adding bacon and other processed meats whenever possible?
There is no definitive answer, of course, because time machines don't exist. But there's actually a pretty good indicator: what happened the last time a major study found eating meat causes cancer.
In 2002, the American Cancer Society released a report that cast the food category in a similar light. It suggested that people limit their consumption of processed and red meats, pointing to studies that showed diets low in both are associated with reduced risks of various types of cancer. What's more, it concluded that diets might be responsible for more than one-third of all cancer deaths in the United States.
The news spread quickly, and the reaction was loud, much as it was last week when the WHO published its study. But the talk was cheap. Americans listened intently, and then continued as they were. Consumption of processed and red meats, along with many other animal proteins, didn't budge, according to data from market research firm NPD Group. In fact, Americans are eating more processed meats today than they were a dozen years ago.
The chart below, courtesy of NPD, shows that, in response to the 2002 report, people haven't slacked off on eating meat.
Why Americans have remained so stubborn about their meat-eating ways is unclear. It's possible that people simply love the animal protein too much. Those who do might seek validation of their affinity in arguments that the evidence of meat's harm is overstated (those arguments are fairly common and not necessarily wrong).
It could also be that we are all too set in our ways. "Humans are creatures of habit for the most part, and are slow to change," Darren Seifer, an analyst at NPD, said.
But what it points to is more of the same: a lot of talk, and a little, if any, action.