You cannot run any dynamically compiled GTK+ programs without including/installing the GTK+ runtime libraries or environment.
What all you can do is include or copy all those required runtime libraries in to the folder where your application reside and create a GTK+ runtime environment. Of course, doesn't matter how small your application file size is, the distribution packages size will increase depending on the required runtime libraries which your application use. To get better understanding, look at the following Windows version
of the applications.
- Very good network protocol analyzer
(Old project name is 'Ethereal' http://www.ethereal.com/
- It is a Vector Graphics Editor
Another way of doing is getting source code of the GTK+ runtime and compile them statically in to your application. But still file size is not going to decrease. Here the GNU LGPL license issue will arise if your binary distribution is not going to give free the source code of the application. If you are interested about license please look in to their specific website.
At last, try to Install windows specific official GTK+ Runtime for commonly available for all GTK+ Applications. This is the recommended way in Win32 environment.
There are few other sites offer readily builded installer version of minimum GTK+ runtime packages for windows as well.
3.5 MB zipped
Look at in the internet for latest version of the installer.