Researchers from Harvard University said Thursday, rising obesity rates means 42% of Americans will be considered obese, fat friends being at the root of the problem.

Which prediction contradicts the findings of other experts who believe USA’s obesity rate has peaked at 34% of the population.

These findings are from the same group reporting in 2007 that said having an obese friend more than doubles your chances of becoming obese, which phenomenon they say is driving the obesity epidemic that will climb slowly but steadily for the next 40 years.

The study is based on the idea obesity is like an infectious disease that spreads and one can catch from one’s friends. Researchers applied a mathematical model to four decades of data from the Framingham study that studied the health and habits of almost an entire town in Massachusetts.

They found some baseline risk of becoming obese based on one’s friends, including a look at the influence of social interactions on obesity in the Framingham study, making researchers conclude obesity rates in USA will top out at 42% of the population.

The research team found in any given year an American adult has a 2% chance of becoming obese, with each social contact with an obese person increasing the risk of becoming obese by 0.5% per year.

But, while fat friends increases the odds of one becoming fat, being friends with thin people has also not been found useful in losing weight.

Being overweight or obese increases the risk of heart disease, diabetes, some cancers, arthritis and other conditions, with obesity related diseases accounting for nearly 10% of medical spending in the US or $147 billion a year.

The study has been published in the journal PLoS Computational Biology.