Posted by Pattie on 5/10/2003 06:17:00 PM


Determining a cause and effect relationship requires three characteristics to be met. Obesity research and/or the reporting of obesity research frequently forgets at least one of these characteristics when asserting that fat causes disease:

1. The proposed cause must occur in time before the proposed effect. This seems simple enough, but in "obesity" research this question is rarely addressed. Did a medical condition occur before weight was gained? This is a difficult question to answer in medical research because the time of diagnosis is not the time the medical condition occurred, it is merely the time when some professional noted the occurrence. So if a fat person presents herself or himself to a medical professional and is discovered to have a medical condition, no one really knows for sure when that condition began. This is especially true since symptoms don't always show up at the onset of the medical condition, so even the person with the condition might not know when it began. Thus, establishing cause and effect relationships between fatness and disease is often compromised from the start.  Simply noting that fat people commonly have a disease does not establish a cause and effect relationship. The
time question must be answered.

2. There must be a significant statistical correlation between the proposed cause and the proposed effect so that changes in the proposed cause result in changes in the proposed effect. This is only one of the conditions for cause and effect, but it is frequently the only one to which press releases pay attention. Media reporting correlations without discussing any of these other factors is distorting the results. You can't conclude that something causes something else simple because a correlation exists. Having said that, you do have to have a correlation to make the case for cause and effect and that correlation should be fairly strong (or you haven't accounted for the cause yet, only part of it). "Obesity" research errs in both ways -- correlation is mistakenly reported as cause AND causes are mistakenly asserted when the correlations are weak.

3. The most important part of determining cause and effect: NO OTHER EXPLANATION IS POSSIBLE. This is the skepticism of science and the part that is skipped all the time. Just because a proposed cause occurs in time before a proposed effect and changes in that proposed cause are correlated to changes in the proposed effect, THAT DOES NOT PROVE CAUSE AND EFFECT. The assumption always is that the proposed cause and effect relationship does not exist. Skeptical questions must be asked to rule out any other possible explanation for the observed relationship. There are some specific alternative explanations to a seemingly cause and effect relationship. These should be checked out before asserting cause and effect.

The next installment of my little science series will discuss these alternative explanations and how they related to "obesity" research. I probably won't get a chance to write more about this for several days because I'm going to Vancouver on business next week.  But I will get back to this, I promise.