In a study using rats, Yaiping Yang of the Lawson Health Research Institute affiliated with The University of Western Ontario found abdominal fat makes a hormone -- Neuropeptide Y, or NPY-- that stimulates fat cell production.

A fat cell cannot replicate itself, the researchers say, but they found NPY increases fat cell number by stimulating the replication of fat cell precursor cells, which then change into fat cells.

"This may lead to a vicious cycle where NPY produced in the brain causes you to eat more and therefore gain more fat around your middle, and then that fat produces more NYP hormone which leads to even more fat cells," study researchers said in a statement.

The researchers said they hope this finding -- that the abdominal fat itself produces the powerful appetite stimulating hormone NYP -- will lead to new therapeutic targets for combating the fat responsible for the "apple -shape" linked to an elevated risk for heart disease, type 2 diabetes, hypertension and some cancers.

The study findings are published in the journal of the Federation of American Societies for Experimental Biology.