http://www.wimp.com/powerfulobesity/
The length exceeds more than 30 seconds but I strongly feel that this is one of the most powerful videos that I have seen. It is a powerful anti-obesity video where it takes you back in time, where the kid first ate french fries. It is disturbing in a good way because now I feel like I strongly think what Fast food does to one child.

https://www.youtube.com/watch?v=DdVfpXSq2nY
This video can kind of make an exception. This video is way different than the first one because it is an informational video were it presents stats. It is a good video but I feel like the first one is effective.