Read this interesting story on how researchers found that applying a small electric current to the brain had lasting effects on increasing math skills. NewsDaily: Electric brain stimulation can improve maths: study
Although I find that fascinating, I'm more interested in how exercise and being fit increases learning ability and cognition. Students' physical fitness associated with academic achievement; organized physical activity
Students in 5th through 7th grades were followed, measuring academic performance as the students progressed through the grades. Fit students scored higher than less fit students.
Students who were less fit in grade 5 but then more fit by grade 7 improved academically. Those who were more fit in grade five but lost fitness by grade 7 showed a decrease in academic scores. Students who maintained their fitness also maintained their higher academic prowess.
Stay fit and we can be as smart as a 5th grader.