Prevention is better than cure provided (which is not always the case) that prevention does less harm than the disease it prevents. Since obesity is now of epidemic proportions all over the world, and it is estimated that in just over a decade’s time there will be 500,000,000 people with type II diabetes consequent upon obesity, prevention of obesity is devoutly to be wished – which is not to say that it will be easy or even possible.

An article in a recent edition of the New England Journal of Medicine asks the question of how early in life prevention of obesity should begin, given that once it is established it is refractory to treatment. Although the epidemic may have peaked in the United States, there is no room for complacency because the proportion of fat people is already enormous. A half of American pregnant women are seriously overweight or outright fat, and fat women tend to have fat children. They gain even more weight during pregnancy, and women who gain weight excessively during pregnancy are especially likely to have fat children.

The article is a typical example of what might be called risk factor medicine. A disease or disorder is found to be associated statistically with some independent variable which may or may not be causally related to that disease or disorder, so that doctors hope that by reducing the prevalence of the risk factor in some way they will also reduce the prevalence of the disease or disorder. Since many of the risk factors are behavioral rather than biological, and there is nothing as difficult to change as human behavior, doctors’ hopes are often frustrated.