How to Search for Forums for a Specific Keyword?

[Stephenson]

I saw some similar stuff in some of the ebooks which I downloaded from here.
But I kinda lost all those ebooks.Can someone help me point out the ways in which to search for all the forums or many of the forums for a specific keyword.
For eg:
if I want to search for forums targeting keyword Weight loss,what am I supposed to type in the Google?
Is it like something lke inurl:forums+keyword with or without quotes or something like that.
Can someone help me point out the right direction.
Thanks

 

[webmast]

A few examples to get you started:

"powered by vbulletin" "weight loss"
"powered by smf" "weight loss"
"powered by phpbb" "weight loss"