Response to Obesity Study Published in New England Journal of Medicine

by Professor Paul F. Campos, University of Colorado

Rocky Mountain News April 2, 2003 - According to the authors of a new study published in the New England Journal of Medicine, "more than 90,000 deaths per year from cancer might be avoided if everyone in the adult population could maintain a body mass index (BMI) under 25.0 throughout life."

Let us consider their evidence for this proposition. The American Cancer Society study from which the authors drew their data actually found the lowest cancer risk among "overweight" men (BMI 25 to 29.9). This fact was omitted from all the major media stories reporting on the study.

Furthermore, among the "obese," (BMI 30 +) the increased risk of cancer death was negligible until subjects reached a BMI of 40 and above. Less than 5% of the adult population is in this category. Yet the media's coverage of this story has emphasized that 65% of the population is supposedly too fat, even though the 73 million Americans currently classified as "overweight" are actually in what the study's data indicates is the lowest risk weight cohort, while the vast majority of their "obese" brethren appear to run little or no increased risk of cancer associated with their weight.

Note that even if cancer was closely associated with increasing weight, it wouldn't necessarily follow that advocating weight loss would be the appropriate response. For example, the New York Times headlined its story on the study "Losing Weight May Prevent Cancer Deaths." Yet this study contained no data on the effects of intentional weight loss on cancer mortality. Glenn Gaesser, a professor of exercise physiology at the University of Virginia, points out why the absence of such data from this study is worth noting.

"Previous American Cancer Society studies have looked into whether intentional weight loss affects cancer risk," he says. "A 1995 ACS study found that an intentional weight loss among overweight women of one to 19 pounds was associated with a 24% to 62% higher risk of cancer mortality, as compared to equally overweight women who were weight-stable. And a 1999 ACS study found that intentional weight loss among men had no association with decreased cancer mortality. Indeed," he points out, "the 1999 ACS study noted a general association between increased cancer mortality and intentional weight loss."

"Why have the authors of this latest ACS study not reported any data on intentional weight loss and cancer mortality rates?" Gaesser asks. (In fact, the new ACS study does not even cite these earlier ACS studies). "Judging from the results of the previous ACS studies, I have a hunch as to why," he says.

That's not all. Paul Ernsberger, an obesity researcher at Case Western Reserve University, points out that, even among the extremely obese, the association the study found between weight and cancer mortality was weak. "In a study of this type anything under a two-fold risk is suspect," he says, "especially given the huge number of subjects involved, and the questionable exclusion criteria the authors employed." For instance, the study excluded everyone who had lost ten or more pounds in the previous year, which means dieters were excluded far more often than non-dieters.

Just as in the war on drugs, the war on fat has reached the point where the systematic distortion of the evidence has become the norm, rather than the exception. The strategies employed in these two wars are strikingly similar: Treat the most extreme cases as typical, ignore all contrary data (there are dozens of studies that indicate cancer mortality decreases with increasing weight), and recommend "solutions" that actually cause the problems they supposedly address. And, as in all wars, truth ends up being the first casualty.