The United States is more than 3 billion pounds overweight, with 65 percent of Americans… The United States is more than 3 billion pounds overweight, with 65 percent of Americans having a weight problem.

Feeding off the importance of such weighty issues, Dr. Ronald Evans gave a lecture, “Nuclear Receptors in Metabolic Disease,” on Tuesday afternoon in Scaife Hall.

Evans discussed a theory among researchers that obesity is just an illusion. Although some researchers believe that weight gain occurs only in people at the high end of the weight spectrum, Evans thinks that individuals in both the high and middle end of the weight spectrum gain weight.

Evans discovered that a superfamily of genes ultimately regulates how lipophilic hormones and drugs govern many developmental and metabolic pathways in animals and humans. Essentially, these genes play a major role in how a person’s body develops.

These findings define a comprehensive model for the control of gene expression, which has led to the discovery and development of drugs for cancer and metabolic diseases such as obesity, hypertension, diabetes and atherosclerosis.

Noting that the number of obese Americans has increased from 21 percent in 1991 to 31 percent in 2000, Evans said that people spend 46 percent of their total food money on prepared food.

When people go on diets, they hope to eat less — but the body doesn’t function that simply. Evans said that eating less can lead to less metabolic burning, which can make it harder to lose weight.

“I went on a diet, swore off drinking and heavy eating, and in 14 days I lost two weeks,” Evans said, using a quote from Joe E. Lewis to demonstrate a popular attitude toward dieting.

For those who haven’t tried dieting, Evans explained that it is easier to gain weight than to lose it.

Evans also discussed the origins of heart disease.

“Heart disease can begin in the embryo, but it almost always begins in early childhood,” Evans said.

Evans’ work led him to a few important conclusions, including that “genetically generated fibers confer resistance to obesity, even in the absence of exercise.”

Another result he found is that a person’s appetite can generally be controlled more easily than his weight.

Some of Dr. Evans’ most recent awards include the 2003 March of Dimes Prize in Developmental Biology and 2003 Alfred P. Sloan Jr. Prize from the General Motors Cancer Research Foundation; he was also the co-recipient of the 2004 Albert Lasker Award for Basic Medical Research.

Evans is the March of Dimes Chair in Developmental and Molecular Biology, professor in the Gene Expression Laboratory, and a Howard Hughes Medical Institute investigator at the Salk Institute for Biological Studies.