If you subscribed through the website
You can unsubscribe via a link on your profile page. You can get there by clicking your username in the sidebar, or directly here: https://www.eatthismuch.com/account/membership/
If you subscribed through iOS
You'll need to unsubscribe via the App Store's subscriptions page. There's a link to it in the app's settings page, or you can find it by going to your phone's Settings -> iTunes & App Store -> Apple ID -> View Apple ID -> Manage (under Subscriptions)
If you subscribed through Google Play (on Android)
You can unsubscribe via the Account Info section of the android app, or directly on Google's payments manager here: http://payments.google.com/
NOTE: If you cancel or unsubscribe, you can still use the remainder of your subscription time, even if you cancel during the free trial.