Less is more? (Kiyoshi Ota/Bloomberg News)

The U.S. Department of Agriculture is preparing to release the latest version of the government's influential dietary guidelines this year, and there could be a major change that accelerates the trend of Americans eating less meat.

The guidelines, which are updated every five years, have traditionally advised Americans about healthy eating choices, eating choices which, until now, have only reflected what the government views as a diet that is healthy for humans. But the panel that advises the government is pushing for the recommendations to reflect what is healthy for the environment, too. Given the huge carbon footprint of meat production, making this change would almost certainly entail lowering the official, government-recommended intake of meat.

Americans, though they are eating less meat than they have in the past, are still fond of steaks, hamburgers, and chicken wings. And the environmental impact of that diet is significant. Carnivores contribute far more to environmental decay than do vegetarians. The livestock industry is responsible for an estimated 15 percent of total global carbon emissions, roughly two-thirds of which is the result of beef production. On a per kilogram basis, the carbon footprint of lamb and beef production is unparalleled.

Meat environmental impact
Source: Environmental Working Group

Meat industry advocates have been battling the prospect of lowered meat intake recommendations for decades. But those battles have largely been waged on the nutritional health front, and the evidence is mixed on whether meat is actually harmful to your health. As a result, the government now recommends that people opt for leaner meat, instead of less meat.

Defending meat on environmental grounds, however, could be much tougher for the industry. Several international and government agencies, including the United Nations, have spelled out the meat industry's massive footprint. And now the USDA could be next with new, government-backed dietary guidelines.

For that reason, several industry players have responded critically to the consideration, both attacking the notion that meat production is environmentally unfriendly and discrediting the idea that environmental concerns should influence the dietary guidelines issued by the government. The North American Meat Institute (NAMI) and National Cattlemen's Beef Association have each issued statements insisting that lean meat should be part of healthy diets and denouncing any suggestion that environmental impact should dictate the recommendations.

"The Dietary Guidelines Advisory Committee’s focus on sustainability is objectionable because it is not within the committee’s expertise," NAMI said in a statement.

A draft of the government panel's advice, which was released last month, calls for the consumption of more plant-based foods and less animal-based ones, because it's "associated with lesser environmental impact than is the current average U.S. diet." Specifically, the draft advises less "red meats" and "processed meats."

Just because the USDA's advisory committee is discussing such recommendations doesn't mean it will ultimately include them in its official findings, which are expected to be delivered to the Agriculture and Health and Human Services departments later this month. Nor does a recommendation by the panel mean the departments will ultimately heed the advice in determining the final guidelines, which are expected to be released later this year. But the they might. And if they do, the impact would be significant.

"Americans don't necessarily heed dietary recommendations," said Janet Riley, the senior vice president of public affairs for the North American Meat Institute. "But where this could have a huge impact is on purchasing programs. The federal feeding programs are significantly impacted by the federal dietary guidelines."

Indeed, the immediate impacts would be substantial. Reducing the recommended amount of meat consumption would reduce, among other things, the amount of meat the industry provides as part of the school lunch program. And overnight, the diets of millions of Americans would have less meat.