But as Jeffrey M. Friedman, M.D., Ph.D., argues in a "Viewpoint" article in a special obesity issue of the journal Science published Feb. 7, obesity cannot be easily explained as simply a breakdown in willpower. Genes and environment, explains the Rockefeller University and Howard Hughes Medical Institute researcher, both play important roles in determining a person's body weight. He points put that "in general, environmental factors account for trends in a population over time, while genetic factors account for most of the differences in weight among individuals in present time.
"While answers are beginning to emerge as to why so many of us are obese, there can be no meaningful discussion on this subject until we resist the impulse to assign blame," writes Friedman, who led the laboratory team that discovered the obesity hormone leptin in 1995. "Nor can we hold to the simple belief that with willpower alone, one can consciously resist the allure of food and precisely control one's weight.
"Instead, we must look at the facts dispassionately and uninfluenced by the numerous competing interests that drive debate on this subject."
The facts, according to Friedman, are: increase in weight does not fully account for the increase in the incidence of obesity; the drive to eat is to a large extent hard-wired and differences in weight are genetically determined; and evolution exerts powerful forces that obese people need to fight in order to lose weight.
An understanding of how genes and environment interact to cause obesity, Friedman urges, requires a broad-based research program that investigates not just the genes but how they interact with the environment.