Eating lettuce "is over three times worse in greenhouse gas emissions than eating bacon," says Prof. Fischbeck.
The study is published in the journal Environment Systems and Decisions and was conducted by researchers from Carnegie Mellon University in Pennsylvania.
As part of the US government's 2015 Dietary Guidelines for Americans, health officials detailed diet recommendations to the US Department of Agriculture (USDA), which called for the adoption of plant-based diets as a way to improve public health.
Additionally, a study published earlier this year suggested consuming a vegetarian diet is linked to reduced risks of colorectal cancer.
However, despite the touted health benefits of a vegetarian diet, researchers from the latest study have found that following the USDA recommendations to consume more fruits and vegetables will be harmful to the environment because these foods have high resource uses and greenhouse gas (GHG) emissions per calorie.
Study author Prof. Paul Fischbeck says eating lettuce "is over three times worse in greenhouse gas emissions than eating bacon," noting that many common vegetables use "more resources per calorie than you would think."
Interestingly, he says vegetables such as eggplant, celery and cucumbers require more resources than pork or chicken.
'Complex relationship between diet and environment'
Prof. Fischbeck and colleagues - Michelle Tom, PhD student, and Prof. Chris Hendrickson - analyzed the food supply chain in order to assess how the US obesity epidemic is affecting the environment.
In detail, they looked at the growing, processing and transporting of food - as well as food sales and household storage - to determine how they impact resources by using energy and water, and how they impact GHG emissions.
Results revealed that keeping the obesity epidemic in check by eating fewer calories positively impacts the environment by reducing energy and water use, and lowering GHG emissions by around 9%.
On the flip side, however, eating the healthier foods as recommended by the US Dietary Guidelines - which includes fruits, vegetables, dairy and seafood - negatively impacts the environment by increasing energy use by 38%, water use by 10% and GHG emissions by 6%.
"Amidst the current overweight and obesity epidemic in the USA, the Dietary Guidelines provide food and beverage recommendations that are intended to help individuals achieve and maintain healthy weight," write the authors.
However, Michelle Tom notes that there is another side to eating healthily:
"There's a complex relationship between diet and the environment. What is good for us health-wise isn't always what's best for the environment. That's important for public officials to know and for them to be cognizant of these tradeoffs as they develop or continue to develop dietary guidelines in the future."
Then again, what is good for the environment is not always best for our health; Medical News Today recently reported on a study that suggested avoiding meat could reduce kidney cancer risks.
Additionally, a report published recently by the World Health Organization (WHO) suggested eating processed meats can cause colorectal cancer.