The keto diet, which is high in fat and low in carbs, and the paleo diet, which is low in grains, processed foods, and refined sugar, had 3-4 times the carbon emissions of the vegan diet. This isn’t surprising when you consider that both keto and paleo tend to be more meat-forward and less legume-based eating patterns. The overall environmental impact of meat from ruminant animals (cows, sheep, goats) is about 100 times that of plant-based foods according to some estimates, due in part to the way these animals digest. And the legumes that both diets eschew have nitrogen-fixing qualities3 that make them beneficial for soil and ecosystem health.
While the health scores should be taken with a grain of salt—and they differed depending on the index used in some cases—it makes sense that a diet that is healthy for the planet tends to be pretty good for us, too.
“Climate change is arguably one of the most pressing problems of our time, and a lot of people are interested in moving to a plant-based diet,” Diego Rose, Ph.D., MPH, the senior author of the study, said in a statement. “Based on our results, that would reduce your footprint and be generally healthy. Our research also shows there’s a way to improve your health and footprint without giving up meat entirely.”