A nation's reading habits predict if its citizens are on their way to being heavier or thinner, a new study shows.

Researchers analyzed foods mentioned in newspaper articles in the New York Times and the London Times over 50 years and statistically correlated them with each country's annual Body Mass Index, or BMI, a measure of obesity.

The number of mentions of sweet snacks was related to higher obesity levels. Meanwhile, vegetable and fruit mentions correlated to less obesity. Salty food mentions were unrelated to obesity levels.

The findings provide public health officials and epidemiologists with new tools to quickly assess the effectiveness of obesity interventions, said Brian Wansink, who co-authored the study, and is director of the Cornell Food and Brand Lab.

"Newspapers are basically crystal balls for obesity," said Wansink. "This is consistent with earlier research showing that positive messages --  'Eat more vegetables and you'll lose weight' -- resonate better with the general public than negative messages, such as 'Eat fewer cookies.’”