Eat less beef, more plant-based foods. Americans, on average, eat more than 200 pounds of meat per person each year — 66 pounds of it beef. By some estimates, we eat an average of two ¼-pound burgers a week. Behind every T-bone, there's a burning trail of fossil fuel. To start, growing the copious amounts of corn needed to feed cattle requires synthetic fertilizers and pesticides made from fossil fuels. It takes 32 pounds of feed to produce 4 pounds of beef. Then there's the matter of planting, harvesting, processing, packaging, and transporting all that feed. Ultimately, it takes ten times the amount of fossil fuels to produce 1 calorie of beef than it takes to produce 1 calorie of grain.

What's more, through their natural digestive process, cows belch huge amounts of methane, an even more potent heat-trapping gas than CO₂. Livestock contribute 18 percent of the planet's total greenhouse-gas emissions (GHG) — more than all the planes, trains, and automobiles combined.

Make a balanced choice: Dine on red meat sparingly, says Geagan. The health benefits — including preventing heart disease, diabetes, and certain cancers — of eating less red meat and more fruits and vegetables are well documented. For starters, try cutting out one or two red meat-based meals per week. Geagan suggests substituting grilled portobello mushrooms for meaty burgers or simmering beans and veggies together to create a hearty chili. (For additional ideas, check out Delicious Living's vegetarian recipe archive.)

Next: Eat whole foods; limit processed products