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Researchers spent 16 years evaluating 900,000 people who were cancer-free when the study began in 1982. They concluded that excess weight may account for 14 percent of all cancer deaths in men and 20 percent of those in women.

"Because of the magnitude and strength of the study, it's irrefutable," said Dr. Donna Ryan, head of clinical research at the Pennington Biomedical Research Center in Baton Rouge. "It's absolutely convincing. And therefore it's frightening."

It raises levels of insulin, prompting the body to create a hormone which causes cells to multiply.

Donna's not thinking well. Looking at the last sentence quoted above, I bet they didn't control for level of physical activity. This has been typical of most of these studies relating body weight to disease and a major confounder in the data. In very large (no pun intended) studies relating weight to morbidity done at the Cooper Institute in Dallas, TX by Stephen Blair and others, much of the morbidity due to excess weight is actually due to the decrease in physical activity that initially led to and reinforced the gain in body fat. Some of these studies have shown that obese adult men who had sufficient activity were much less likely to die from a variety of causes than were lean men who were physically inactive.

In a meeting for the students in our department when Dr. Blair was here as the featured speaker at the annual Lydia J. Roberts Seminar, he told us that he and others had questioned researchers about why they had not included physical activity level as a variable to be controlled in their experiments. They just hadn't thought it was important. Think of that. A variable that determines one's metabolic state, one's levels of endocrine signaling, one's level of cardiovascular fitness was something that they just didn't much thought to. Donna needs to remember that what she doesn't know can be as important as what she thinks she does know.