Aimono

There are many stories on how the trend started.  Some people said that it started in Mixi, a popular social networking website in Japan.  After appearing in magazine articles, books and on TV programs, this is the most popular diet in Japan right now.   The most popular book has sold more than 700,000 copies and there are many other books on the market.

Does it work?

I have not tried it myself and I do not know anybody who has tried it.  Although according to the news, every other person in Japan is eating bananas.

The morning banana diet
There are many variations of this diet.

The diet is super simple:
Eat one or two bananas for breakfast.  If 20 minutes later you feel hungry
you can eat other foods
Eat normal lunch and dinner (no dessert).
Drink only small amounts of room temperature water with your meals.
Try to eat dinner by 6:00 PM
Eat slowly and enjoy every bite
Sweet snack at 3:00 PM
Stop eating at 8:00 PM
Do not drink a lot of water
Try to go to bed early, the latest by midnight

My opinion
This is a fad diet; there have been other similar diets in Japan such as
the Nato diet (Nato is a popular Japanese dish of fermented soy beans).  I
am skeptical, but it has some advantages for people who do not eat
breakfast; it forces them to eat a banana, not the best breakfast but better
than an empty stomach.  The recommendation to eat slowly and drink only
small amounts of water during meals is also good advice as is the advice to have
dinner early and get enough sleep.

You can read the full diet in English on this site:
http://morningbanana.com/

There is also an interesting article in the online edition of the Japan
Times http://search.japantimes.co.jp/cgi-bin/nn20081007f1.html