When you’re a “green” consultant (whose last name coincidentally is Greener), people ask you a lot of questions about saving the planet. Especially around Earth Day. Of course there are the obvious ways to do it‚Äîfollow the reduce, reuse and recycle mantra‚Ķ. (notice, it’s not recycle, reduce, reuse‚Ķ..) but there is a not so subtle thing we Americans can do for Earth Day to significantly impact climate change.

 Reduce our country’s obesity level.

Yes, if we collectively lose weight as a country‚Äîeat better, get more exercise, and make better choices‚Äîwe’ll be healthier as a population, but also as a planet.

Two years ago, the London School of Hygiene and Tropical Medicine published a study showing that, because of food production and transportation factors, a population of heavier people contributes more harmful gases to the planet than a population of people at a healthy weight.

Americans today are individually consuming hundreds more calories a day than a generation ago.  The more food that’s consumed, the more food production is required, and the more CO2 is created. Today’s Americans are eating more processed food too, requiring more CO2 to make it, move it, refrigerate it, and heat it.

And then there’s physical activity‚ or lack thereof. The larger we become, the more fuel is required to move us in cars, in planes, buses, etc.  A study published in The Engineering Economistestimated Americans are burning nearly 1 billion more gallons of gasoline each year than they did in 1960 because of increasing obesity rates. Simply put, more weight in the car means lower gas mileage.

The more overweight we become, the less likely we are to walk or bike those short distances. And it’s the first few miles that are actually the most polluting, since most vehicle pollution control devices only work well after several miles of travel.

The study went on to say that in 2009, an obese individual was responsible for the release of more than a metric tonne more carbon dioxide every single year than a healthy weight person. How much is a metric tonne of CO2?  It’s like burning an extra 112 gallons of gasoline. Compared with a population of healthy weight people, a population with 40% obesity requires 19% more food energy for its total energy expenditure. We could lower our climate change impact by 19% by getting healthier, eating better and feeling better.

Together we can make the healthier choices also the new greener choices‚ÄîVeggie Monday’s, walking more, and choosing more local fresh foods are just a few examples.

Instead of waiting until January to start our healthy new year’s resolution, this year let’s start on Earth Day. It will not only make us healthier, but it will also make our planet a healthier place.

Catherine Greener is co-founder and principal of ClearGreen Advisors, a Boulder-based sustainability strategy consultant group. Her clients include Walmart, Nissan, Proctor & Gamble, Fedex, Shell as well as many start-up operations.