Hara hachi bu

Hara hachi bu (腹八分), or hara hachi bunme (and sometimes misspelled hari hachi bu), is a Confucian teaching that instructs people to eat until they are 80 percent full. Roughly, in English the Japanese phrase translates to, "Eat until you are eight parts (out of ten) full". or "belly 80 percent full".

Okinawans
As of the early 21st century, Okinawans in Japan, through practicing hara hachi bu, are the only human population to have a self-imposed habit of calorie restriction. They consume about 1,800 to 1,900 calories per day. Their typical body mass index (BMI) is about 18 to 22, compared to a typical BMI of 26 or 27 for adults over 60 in the United States. Okinawa has the world's highest proportion of centenarians, at approximately 50 per 100,000 people.

Biochemist Clive McCay, a professor at Cornell University in the 1930s, reported that significant calorie restriction prolonged life in laboratory animals. Authors Bradley and Craig Wilcox and Makoto Suzuke believe that hara hachi bu may act as a form of calorie restriction, thus extending practitioners' life expectancy. They believe hara hachi bu assists in keeping the average Okinawan's BMI low, and this is thought to be due to the delay in the stomach stretch receptors that help signal satiety; The result of not practicing "hara hachi bu" is a constant stretching of the stomach which in turn increases the amount of food needed to feel full.

Influence
In the 1965 book Three Pillars of Zen, the author quotes Hakuun Yasutani in his lecture for zazen beginners as telling his students about the book Zazen Yojinki (Precautions to Observe in Zazen), written circa 1300, which advises practitioners to eat about two-thirds of their capacity. Yasutani advises his students to eat only eighty percent of their capacity, and he repeats a Japanese proverb: "eight parts of a full stomach sustain the man; the other two sustain the doctor".

Hara hachi bu was popularized in the United States by a variety of modern books on diet and longevity.