Boston: The obesity rate in the US will continue to rise until 42 per cent of the country`s adults become obese, their contact with overweight people being a reason for its increase, a recent study has said.
America`s obesity epidemic won`t plateau until at least 42 per cent of adults are obese," the study conducted by Harvard researchers said.
Published in the journal PLoS Computational Biology, the study further added that obesity is contagious and the more obese friends one has, the more likely one is to become fatter.
"Our analysis suggests that while people have gotten better at gaining weight since 1971, they have not gotten any better at losing weight," it said.
The study`s lead author Alison Hill, a graduate student in Harvard`s Programme for Evolutionary Dynamics and in the Harvard-MIT Division of Health Sciences and Technology, said the rate of weight gain due to social transmission - that is from person to person - has also grown quite rapidly.
The Harvard scientists said proliferation of obesity among American adults in recent decades owes in large part to its accelerating spread via social networks.
A non-obese American adult has a two per cent chance of becoming obese in any given year. This number rises by 0.5 percentage points with each obese social contact, meaning that four obese contacts doubles the risk of becoming obese.
The projections by Hill are a "best-case scenario," which means that America`s obesity rate could rise above 42 per cent of adults.
The findings contradict recent assertions by some experts that the US obesity rate, which has been at 34 per cent for the past five years, may have peaked.
However, the silver lining is that Hill`s model suggests the US population may not reach this level for another 40 years, making the future rate of increase much more gradual
than over the past 40 years.
Only 14 per cent of the Framingham study participants were obese in 1971, but by 2000 that number had reached 30 per cent.
About 34 per cent of American adults are overweight but not obese, according to the federal government`s Centers for Disease Control and Prevention.
Researchers derived the estimate by applying mathematical modeling to 40 years of Framingham Heart Study data, which is a study of the health and habits of several generations of people in a single Massachusetts town.