Evidence from decades of discrimination studies has led Mark V. Roehling, an associate professor at the School of Labor and Industrial Relations at Michigan State University, to the conclusion that there is “consistent evidence of weight discrimination.”

One factor is that some employers do not want to be burdened with higher health insurance costs. Other times it is a matter of appearances or a belief that “people of size,” as Mr. Roehling terms the obese, are lazy, weak-willed or considered too unattractive to interact with customers. He has found that some employers are upfront about it, even in Michigan, which is the only state that outlaws weight discrimination.

While conducting research, he said, he was told by a personnel manager, who himself was overweight, that the company would not hire overweight people, even after Mr. Roehling told him that was illegal. The bias is more pronounced toward white women than white men, Mr. Roehling said: “Blacks are more accepting of large people and whites are more accepting of overweight black females.”

Mr. Roehling is convinced that weight bias is stronger than bias stemming from race. You can test that thesis yourself with the Implicit Association Test, at implicit.harvard.edu/implicit. It was created by researchers at Harvard, the University of Virginia and the University of Washington to plumb an individual’s attitude toward race, ethnicity and religion. Take the test for prejudice against overweight people and compare your result against the similar test for race.

Brian A. Nosek, a psychology professor at the University of Virginia who helped develop it, said that test results showed that bias against blacks and the overweight was about equal, but that while people rarely admit to race bias, they freely admit to weight bias. “There is no social sanction against saying you don’t like fat people,” Mr. Nosek said.

The weight penalties come in other forms as well. Sociologists have long noted that in developed countries, the higher-status people tend to be thin and the lower- status ones are fat. “That heavier people have a harder time getting married is pretty well supported,” said Jeffery Sobal, a professor at Cornell University who has studied obesity. Marriage can be crucial in wealth creation, especially when a person “marries up” to someone with money or a higher education. That may be a rarer occurrence for the obese. “There is a stigma against the overweight that plays out in the social class world,” he said.

The end result? The obese accumulate only about half the assets of the normal-size American, said Mr. Zagorsky, the Ohio State University research scientist. He matched B.M.I. and wealth data in the National Longitudinal Survey of Youth, a multiyear sampling done by the Bureau of Labor Statistics, and found that for every one-point increase in the index, net worth dropped by $1,000. The typical female baby boomer, he said, earned $313.70 less annually for every one-point increase in her B.M.I., while the typical male earned $161.30 less for every point.