Overweight Americans are eating their way to an early grave in more ways than people realize. While many may know that excess pounds raise the risk of heart disease, hypertension, diabetes, stroke, arthritis, gallbladder disease and other debilitating and sometimes fatal health problems, now a host of cancers can be firmly added to the list.
No longer is the relationship of excess weight to cancer restricted to just a few cancers like breast and uterine, influenced by hormones produced in body fat.
Rather, as a newly published 16-year study by the American Cancer Society has revealed, deaths from a wide variety of cancers -- including those of the colon and rectum, esophagus, pancreas, kidney, gallbladder, ovary, cervix, liver and prostate, as well as multiple myeloma and non-Hodgkin's lymphoma -- are also linked to excess weight and obesity.
For only a few cancers -- those of the lungs, bladder and brain, in addition to melanoma -- was no link found to excess weight.
In fact, heavier men and women were less likely to die of lung cancer than those of normal weight, probably because smokers tend to be thinner but are also much more likely to die of lung cancer than nonsmokers. When deaths among only those who had never smoked were analyzed, being overweight was no longer protective.
The study, published on April 24 in The New England Journal of Medicine, found a direct relationship between the amount of excess weight and the risk of death from most cancers. In other words, the higher the body-mass index, or BMI, a measure of weight in relation to height, the greater the risk of cancer death.
Thus, while an overweight man with a body-mass index of 25 to 30 has only a 13 percent greater risk of dying of liver cancer than a man of normal weight (index of less than 25), the risk is almost doubled for a man with an index of 30 to 35 and is four and a half times as great for a man with an index of 35 to 40.
Likewise for women. The risk of death from breast cancer is 34 percent higher in women with a BMI of 25 to 30, 63 percent higher in those with an index of 30 to 35, 70 percent higher in those with an index of 35 to 40 and more than twice as high in those with an index over 40.
Deaths from uterine cancer showed a similar pattern, with a sixfold increase in risk among women with a body-mass index of over 40.
All told, the heaviest men had death rates from all cancers that were 52 percent higher, and the heaviest women had death rates 62 percent higher than occurred among those of normal weight.
The study followed 900,000 men and women from 1982, when all were healthy, to 1998. It estimated that 90,000 cancer deaths each year could be prevented if all adults maintained normal body weights. Being overweight or obese "could account for 14 percent of all deaths from cancer in men and 20 percent of those in women," the authors, headed by Dr Eugenia Calle, concluded.
The cancer society authors say this is a conservative estimate derived from findings that include current and former smokers.
If only those who never smoked are taken into account, the cancer risk associated with excess weight is even greater, the authors add.
A growing body of biological evidence could explain these observed relationships between cancer and body weight.
As the authors point out, "potential biologic mechanisms include increased levels of endogenous hormones -- sex steroids, insulin and insulin-like Growth Factor I -- associated with overweight and obesity."