"There is a lack of investment in sporting infrastructure," he said, "and an influx of American junk food, which is why lots of people are unhealthy.
"We built a league from scratch, which was the most fundamental, and difficult, stage." Mr Watson, 27, who is now back in Hammersmith after his 15-month trip, has written a book, Up Pohnpei, about his experiences.
He said he became disillusioned with football after playing semi-professionally in England and realised he would have to travel to make a difference.