how come it stopped working after college?

Well I don't know about anyone else, it still works for me, but just like with a lot of other things with age, not as well. (In my later 20's, I added lots of late nights with lots of  Johnnie Walker Black, wine, and rich restaurant meals provided by a boyfriend with ill gotten cash combined with working 4 jobs. Wait, isn't that sometimes alluded to as the Keith Richards diet?)

Actually the study sounds extremely interesting to me, like they are onto something that's gonna turn some more of the more conventional wisdom about blood sugar and the brain on it's head. I just don't like the "sugar makes you stupid" spin this article put on it:

"The second group of rats navigated the maze much faster than the rats that did not receive omega-3 fatty acids," Gomez-Pinilla said. "The DHA-deprived animals were slower, and their brains showed a decline in synaptic activity. Their brain cells had trouble signaling each other, disrupting the rats' ability to think clearly and recall the route they'd learned six weeks earlier."

The DHA-deprived rats also developed signs of resistance to insulin, a hormone that controls blood sugar and regulates synaptic function in the brain. A closer look at the rats' brain tissue suggested that insulin had lost much of its power to influence the brain cells.

It's really about Omega 3 fats as much as it's about fructose sugar, maybe more so.

As someone who has long struggled with sleepiness both from effects of low blood pressure, and an inherited disposition to being a night owl with subsequent jet-lag-like brain-fog when trying to adhere to the rest of the world's schedule, and who also has discovered on my own that sugar combined with fat gives me a long-lasting boost while it would make others crash, I might be looking up more on the study.