In one study, employers were given resumes with photos for available positions. Thin women were often favored over overweight women even when the overweight women was more qualified. When employers were questioned about their decisions, they often said that overweight individuals were lazy, sloppy, and not good workers. Reality shows no correlation between obesity and the performance of most job tasks. Obviously certain jobs have physical fitness requirements, but even for these jobs, simply being overweight may not correlate with a low fitness level. Assumptions should not be made about applicants based on their weight alone.
I think the most shocking research result that I saw was one employer survey where 16% of the respondents said that they would not hire an overweight woman under any circumstances! Knowing that there is a huge heredity component to obesity and that very few people are successful at irradicating the condition in spite of a huge drive by any obese person that I have known, I feel that employers need to stop judging and start hiring the best people for the jobs.