Xamarin.Forms.Shared project creating APK with larger size.

Hi there,
I am using Xamarin.Forms.Shared project to develop android application using Visual studio 2015. I followed this link Publishing application for deploying the application. I got 8.5MB size of APK after setting architecture 'armeabi-v7a' in release mode (If I choose shared runtime it will become 11MB). But If I developed the same application using native (Blank app) android from visual studio, the APK size will reduced to 3.8MB. What is the causes of this problem. Am I doing anything wrong ? or Xamarin.Forms.Shared increases the APK size ? Help me . thanks