American voters may be biased against heavier candidates, a new study by researchers from Michigan State University suggests. 

Mark Roehling, a weight bias expert at the said University led an investigation, looking for a correlation between candidate weight and vote totals. Roehling and his team found overweight candidates received fewer votes than thinner aspirants for the office. 

Weight bias has previously been shown to exist in a wide variety of circumstances, including business, school and entertainment, as per Roehling. This new study is the first to provide direct evidence of such a bias in voting patterns.

"We found weight had a significant effect on voting behavior. Additionally, the greater size disparity between candidates, the greater the vote share of the more slender candidate," Roehling said. 

Patricia Roehling, a psychology professor at Hope College, joined her husband, as they studied voting patterns in the U.S. Senate elections in 2008 and 2012. The research included data from 126 primary and general elections. Each candidate was examined in color photographs and ranked as normal weight, overweight or obese. 

The study showed a clear correlation between body size and vote totals. 

"Obese candidates were largely absent from the pool of candidates in both the primary and general elections... heavier candidates tended to receive lower vote share than their thinner counterparts," the Roehlings reported in the article announcing their findings. 

The effect was especially pronounced for overweight women, who suffered at the polls worse than overweight men. This suggests that weight bias against slightly overweight candidates is influenced by gender of the office seeker, not just their relative size. 

"The study provides evidence that the bias and discrimination against the overweight and obese that has been documented in the areas of employment, education, health care and social situations also extends to the electoral process in the United States," Roehling stated in a university press release. 

Research assistants were used to determine the weight class of each candidate, using an established method. 

More than a decade before the commercial availability of television, William Howard Taft, was elected President of the United States in the election of 1908. He was certainly the heaviest person to ever serve as commander-in-chief. Today, New Jersey governor Chris Christie, who has joked about his own weight, is considered a leading potential candidate for president in 2016. 

Roehling worked as a civil attorney representing employment cases like discrimination and wrongful discharge before becoming a university professor. 

The study was published in the journal Equality, Diversity and Inclusion.