I don't know what is your 'predefined list'.
Look at the following code snippet, the hope can help you:
var mDoc = app.activeDocument, mFind,mChange=0;
//step1
app.findGrepPreferences = app.changeGrepPreferences = null;
app.findGrepPreferences.findWhat = '\\d+kg';
mFind=mDoc.findGrep();
//step2
for(var i=0;i<mFind.length;i++) {
app.findGrepPreferences = app.changeGrepPreferences = null;
app.findGrepPreferences.findWhat = '\\d+';
app.changeGrepPreferences.changeTo = '$0';
var re=mFind[i].changeGrep();
mChange+=re.length;
}
app.findGrepPreferences = app.changeGrepPreferences = null;
alert("find:"+mFind.length+",change:"+mChange);