The Notebook star has become a leading celebrity green activist and she has launched a website, GreenIsSexy.org, to help raise awareness about clothing alternatives and better ways to serve the environment.
And, as well as suggesting people stop running water while they brush their teeth, McAdams has a few quirky ideas too.
She tells WENN, "A sexy green thing to do is to wear bamboo underwear! They sound quite painful but they’re actually quite soft. I’ve also got soy underwear!"
She adds, "Our philosophy on the website is not to have green guilt necessarily; just do what you feel comfortable with and you’d be surprised how you feel the positive affects. We’re coming on our two-year anniversary of GreenIsSexy.org and the environmental community has really opened up online.
"That’s the amazing thing about the Internet - for all the problems and concerns, the relationships you can develop with people who are on the same wavelength and deeply care about the same things is immediate and it’s vast."