Thursday, August 23, 2007

Facts on body fat and heart attacks

happy couple
For an average person of average age with a body mass index (BMI) between 19 and 25, the risk of suffering from coronary heart disease is about 9 percent. Under the same average conditions, but with a body mass index of 30 and more, the risk of heart disease is increased by a relative amount somewhere between ten and a hundred percent - with a likeliness of 95 percent. This increase will push the absolute risk from 9 to 10 percent in the best case or from 9 to 18 percent in the worst case. (Source: A consensus paper of the Swiss Expert Group on Obesity and Metabolism, 2006)

These figures are just correlations and tell us absolutely nothing about a possible cause. Thus, if a so-called obese person manages to lose weight, it is quite unlikely that this will reduce the risk of a heart disease. As far as I know, all these experts advising people they should lose weight have no hard facts to prove that this really reduces the risk of a heart attack or other diseases.

A thought experiment on weight loss

Just let me do a little thought experiment here. I'll try to assume conditions that are in favour of weight loss adepts. I do not share them. I just assume that half of the risk increase should be directly attributable to body fat and that it is completely reversible by weight loss. I also assume that there is such a thing as an average person and that general recommendations can be drawn from the statistics.

First step: The relative risk increase that may be prevented by weight loss is between 5 and 50 percent which translates to an absolute risk increase between 0.5 and 4.5 percent - but only if our average person manages to reduce his or her body mass index by ten points, let's say from 35 down to 25.

Second step: Most weight loss trials show BMI reductions of about 2 points, but let's be generous and assume a loss of 5 BMI points. This is half of the required amount for the above risk increase prevention. Let's assume further that half of the reduction will bring half of the preventive effect, that is, between 0.25 and 2.25 of the absolute risk that could be prevented by the weight loss.

Conclusion: Given the fact that I have set the conditions in favour of the weight loss adepts, this outcome of my thought experiment is quite pathetic.

Photo credit: flickr.com/photos/guccibear2005/15232731/

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