The rationale: eating more vegetables and less meat lowers your carbon footprint. Our reliance on fuel, fertilizer, the huge swaths of land required to raise animals and the methane, which is a by product of animal waste, all contribute to global warming.
The PB&J folks certainly aren’t the only ones pointing out that a low-carb diet means more than just scarfing protein three times a day. The Center for Science in the Public interest even has a Eating Green calculator that helps you determine how your eating habits impact the environment. So go ahead, make a peanut butter and jelly sandwich and see if you can shrink your carbon footprint even just a little.