The environment doesn't appreciate our meat obsession.

The average meat-eater in the U.S. is responsible for almost twice as much global warming as the average vegetarian, and close to three times that of the average vegan, according to a study (pdf) published this month in the journal Climatic Change.

The study, which was carried out at Oxford University, surveyed the diets of some 60,000 individuals (more than 2,000 vegans, 15,000 vegetarians, 8,000 fish-eaters, and nearly 30,000 meat-eaters). Heavy meat-eaters were defined as those who consume more than 3.5 ounces of meat per day—making the average American meat-eater (who consumes roughly four ounces per day) a heavy meat-eater. Low meat-eaters were those who eat fewer than 1.76 ounces. And medium meat-eaters were those whose consumption fell somewhere in between.

The difference found in diet-driven carbon footprints was significant. Halve your meat intake, and you could cut your carbon footprint by more than 35 percent; stick to fish, and you could cut it by nearer to 50 percent; go vegan, and the difference could be 60%.

The variations were so drastic that the study's authors suggested that countries should consider revising their definition of a sustainable diet. "National governments that are considering an update of dietary recommendations in order to define a ‘healthy, sustainable diet’ must incorporate the recommendation to lower the consumption of animal-based products," the study says.

The livestock industry is responsible for roughly 15 percent of global carbon emissions. And the resources necessary to produce even the smallest amounts of market ready meat—like, say, a quarter pound hamburger—are staggering.

The good news is that while Americans might still eat more meat than mother nature would prefer, they are scaling back, and especially so with the most environmentally unfriendly kind—per capita beef consumption has fallen by 36 percent since its peak in 1976, according to data from the USDA. The bad news is that the rest of the world appears to be headed in the opposite direction. Global demand for meat is expected to grow by more than 70 percent by 2050, largely driven by burgeoning middle classes in the developing world. Couple that with the potential for changing health narratives in the U.S.—some of which now tout red meat (and fats, in general) as healthier than once thought—and even Americans could find themselves putting more meat on their plates in the future.