Newswise — See any successful overweight politicians lately? If so, they are bucking the odds. Researchers at Hope College and Michigan State University have found evidence of voter bias against hefty candidates for U.S. Senate after controlling for other factors.

“Heavier candidates tended to receive lower vote share than their thinner counterparts and the larger the size difference between the candidates, the larger the vote share discrepancy,” says Patricia V. Roehling, professor of psychology at Hope College in Holland, Michigan.

The upshot: due to bias against overweight political candidates, as much as one-third of the U.S. population is likely to be excluded from being elected to a major political office.

“This study is the first to use election data to examine whether bias based on size extends to the electoral process,” Patricia Roehling reports.

She and a team of students from Hope College, and Mark Roehling of the Department of Human Resources and Industrial and Labor Relations at Michigan State, used data from 49 elections in 2008 and 77 elections in 2012.

They examined pictures taken from candidate websites and estimated the size of each candidate for Senate in both primary and general elections. Each candidate was rated on a scale ranging from obese to underweight. They looked at 158 male candidates and 32 females.

They examined the vote totals for each candidate and, using multivariate regression analysis, controlled for variables such as age, gender, incumbency, and other factors. The result: the more slender the candidate, the greater his or her vote share.

They also found evidence of self-selection in the pool of candidates for Senate. Obese people were almost absent from the study. Only four percent of the men and none of the women were rated obese. Compare that with the general population where 34 percent of U.S. males and 38 percent of females are considered obese.

It was a different story for men labeled as overweight but not obese. Forty-one percent of the male Senate candidates were overweight. Only 16 percent of the women were in that category, however, with 84 percent being in the normal weight range.

“These findings suggest that overweight females are more likely to be excluded from candidacy than are overweight males,” Patricia Roehling says. This supported one of the study’s hypotheses that women candidates would experience a greater weight bias than men.

The research is detailed in an article in Equality, Diversity and Inclusion, an International Journal published in May. The article is titled “Weight Bias in U.S. Candidate Selection and Election.”