Typically, "herbivore men" are in their 20s and 30s, and believe that friendship without sex can exist between men and women, Fukasawa said.
The term has become a buzzword in Japan. Many people in Tokyo's Harajuku neighborhood were familiar with "herbivore men" -- and had opinions about them.
Shigeyuki Nagayama said such men were not eager to find girlfriends and tend to be clumsy in love, and he admitted he seemed to fit the mold himself.
"My father always asks me if I got a girlfriend. He tells me I'm no good because I can't get a girlfriend."
Midori Saida, a 24-year-old woman sporting oversized aviators and her dyed brown hair in long ringlets, said "herbivore men" were "flaky and weak."
"We like manly men," she said. "We are not interested in those boys -- at all."
Takahito Kaji, 21, said he has been told he is "totally herbivorous."
"Herbivorous boys are fragile, do not have a stocky body -- skinny."
Fukasawa said Japanese men from the baby boomer generation were typically aggressive and proactive when it came to romance and sex. But as a result of growing up during Japan's troubled economy in the 1990s, their children's generation was not as assertive and goal-oriented. Their outlook came, in part, from seeing their fathers' model of masculinity falter even as Japanese women gained more lifestyle options.
Former CNN intern Junichiro Hori, a self-described herbivore, said the idea goes beyond looks and attitudes toward sex.
"Some guys still try to be manly and try to be like strong and stuff, but you know personally I'm not afraid to show my vulnerability because being vulnerable or being sensitive is not a weakness."
Older generations of Japanese men are not happy about the changes. At a bar frequented by businessmen after work, one man said: "You need to be carnivorous when you make decisions in your life. You should be proactive, not passive."
