"They have been termed invisible, underscoring the fact their plight is unseen and unheard," the WFP said in a study released days after Bangladesh's Muhammad Yunus won the Nobel Peace prize for finding innovative ways to fight poverty.
Yunus's Grameen Bank has given micro-loans to 6.7 million rural people, 97 percent of them women.
The WFP said Bangladesh's rural poor are "extremely marginalized, chronically hungry, mostly (families) headed by females and are functionally landless with few income earners in the family and large numbers of dependants".
It said that among the invisible poor, 53 percent of households are food insecure year-round, and another 21 percent for more than half the year.
"Chronic food insecurity has been associated with a poor-quality diet and an inability to access adequate food for family throughout the year," it added.
"These findings allow us to better identify households in greatest need. Our responsibility is to contribute to making the invisible poor 'visible'," WFP country representative Douglas Broderick said.
The government's annual economic survey said in June that some 58 percent of microcredit beneficiaries have emerged from poverty.
According to the government's 2005 household survey, 40 percent of the country's 144 million people live below the poverty line even though the country has logged over five per cent annual growth since the early 1990s.
Most of the poor live in the rural areas, home to 70 percent of the nation's population.

Copyright AFP (Agence France-Presse), 2006