Wednesday, November 02, 2005

The Obesity Cancer Connection

Reuters Health reported today that a high number of cancer is due to obesity. The data comes from a review of published studies, updates to the International Agency for Research on Cancer (IARC) report from 2002, and data from the Nurses' Health Study II by researchers at the Harvard School of Public Health.

If no one was overweight or obese, the data shows we would avoid:
  • 14% of colon cancers (14,000 cases)
  • 11% of breast cancer (over 18,000 cases)
  • 49% of endometrial cancer (almost 20,000 cases)
  • 31% of kidney cancer (over 11,000 cases)
  • 39% of esophageal cancer (5,500 cases)
  • 14% percent of pancreas cancers (4,500 cases)
  • 20% of non-Hodgkin lymphoma cases (over 11,000 cases)
  • 17% of multiple myeloma cases

Dr. Graham Coldtiz, from the Harvard School of Public Health stated that "We can clearly conclude that adult overweight and obesity cause cancer, and increasing rates of obesity in the US are continuing to drive up the burden of these cancers."

That's a very strong statement - that obesity causes cancer.

Is it true though?

In my mind it is a very questionable conclusion, stated unequivocally, since it fails to address what causes obesity. It's like trying to determine which came first, the chicken or the egg.

While it is very possible, and probably even true, that a high level of excess body fat - obesity - does actually cause some cancers...generalizing that obesity is the cause of so many cancers misses the real underlying cause in too many others who are diagnoised with cancer - a poor diet. A diet so bankrupt in nutrients that even with more calories than required (which caused the obesity) still leaves the body vulnerable to disease and degeneration.

To me this is the start of a questionable precedent in our understanding of the disease process which may turn our focus away from the very important issue of what is causing obesity, which is causing the cancers.

In too many cases, obesity is a "result of" something else, and that something else is also what causes cancer - poor diet.

1 comment:

  1. It is dissapointing that a Harvard Research doctor has such a limited understanding of statistics that he confuses correlation with causation. If obesity caused cancer then there would be a dose response, i.e the more obese the person
    the greater the cancer rate. Also as you point out he does not give a mechanism by obesity directly causes cancer, for example fat cell secreting a cancer promoting substance. More likely, he knows statistics but want to give quotes that are media-genic. Too bad, another opportunity missed to educate the public on real science and the scientific method. By the way, love your blog especially the emphasis on the weaknesses of the calorie theory and the importance of meeting known nutritional requirements, i.e essential fatty acids, proteins, vitamins, etc. It is kind of amazing that nutritionists have apparently forgotten how to do this, but instead insist that all that's needed is to consume less fat.