I ate one of these with a cup of tea for breakfast on Saturday and am only feeling like myself today. I don't wish to go into the horrifying details, which included being so bloated by noon that I couldn't wear any of my clothes except a wrap skirt to show houses. I went to google to see if the bars were the problem or if it was some kind of stomach virus, and came across this site. Get ready to laugh until you cry at some of the stories.
http://www.pleasegodno.com/index.php?/archives/66-Fiber-One-Bars-make-me-Fart.html