request.post({
  url: 'https://usXX.api.mailchimp.com/3.0/lists/xxxxxxx/members',
  headers: {
    'Content-Type': 'application/json',
    'Authorization': 'Basic xxxxxxxxxxxxxxxxxxxxxxxxx-usXX'
  },
  form: JSON.stringify({
    email_address: req.body.email,
    status: 'subscribed',
    interests: { 'xxxxxxx': true } // Interest Group
  })
}, function(err, httpResponse, body) {
  res.send(body);
});