The Japanese phrase is "soushoku-kei" (草食系), and it's come to refer to a generation of less masculine males who are less interested in pursuing dates and more interested in themselves.
Powell noted that Japan does have a tough road ahead of itself: picking either a strong country with strong economic growth or a weak country with low growth, but still one with happiness. The general also noted that there are those youth who are more interested in reading comics and playing video games than relations with real people.
In all fairness, however, Japan isn't exactly alone in this regard.
The general says that if Japanese youth spend all their time reading comics and sending text messages, they can't solve the country's problems. His message for Japanese youth is that they are essential for the country's future, and they shouldn't fritter their time away. They need toughen up and, um, take in more protein.
Online in Japan, the reaction has ranged from "I like Powell" to mocking "Thanks Powell!" as well as from "I don't want to be told this by a nation of fat people" to "Americans should eat more vegetables".
Some even wondered if there was something lost in translation with Powell thinking that the "herbivore men" term actually referred to individuals who only ate greens. Or maybe it was the stereotype that Japanese people eat only fish and vegetables. Others wondered if the Japanese media goaded him into even talking about this.
Powell's intentions were probably in the right place, and I'd like to see his original English language comments. However, Japan isn't the only country staring down a rapidly aging population, massive government debt, and a broken political system. The U.S. is, too. But, the U.S. is far more open to immigration than Japan has traditionally been. It has much more land and many more natural resources than Japan does. It also has a massive military industrial complex that Japan doesn't. Both have a tough road ahead.