A long article, but with some useful points, I think.


http://www.techcentralstation.com/081705E.html

...The answer, which many will find surprising, is that after over
fifty years of international data there is not good scientific support
for the claim that lifestyle changes prevent diseases or increase
longevity. Take, for example, one of the most extensive and publicized
efforts in health promotion of all time, the Mr Fit (Multiple Risk
Factor Intervention Trial) which was specifically designed to establish
the truth of health promotion by showing that heart disease and cancer
could be reduced through reducing blood pressure, cholesterol, and
smoking. After sixteen years of study, the intervention groups, which
had received extensive assistance with exercise, changing diet and
smoking cessation, had results which were not significantly better than
the group that had received none of these "health promotion"
interventions. Indeed, the intervention group, despite lower rates of
smoking, actually had higher rates of lung cancer. What MR Fit showed
was precisely how lifestyle interventions failed to reduce mortality
from multifactoral diseases like cancer and heart disease.

Nor was Mr Fit a scientific fluke. Consider the Framingham study...