[6][7][clarification needed] The mechanism responsible for this reversed association is unknown, but it has been theorized that, in chronic kidney disease patients, "The common occurrence of persistent inflammation and protein energy wasting in advanced CKD [chronic kidney disease] seems to a large extent to account for this paradoxical association between traditional risk factors and CV [cardiovascular] outcomes in this patient population.
[9] The obesity paradox (excluding the cholesterol paradox) was first described in 1999 in overweight and obese people undergoing hemodialysis,[10] and has subsequently been found in those with heart failure,[5][11][12] myocardial infarction,[13] acute coronary syndrome,[14] chronic obstructive pulmonary disease (COPD),[15] pulmonary embolisms,[16] and in older nursing home residents.
[22][23] One study found that the improved survival could be explained by the more aggressive treatment obese people receive after a cardiac event.
[24] Another found that if one takes into account COPD in those with peripheral artery disease, the benefit of obesity no longer exists.
[29][30] Since smokers, who are subject to higher mortality rates, also tend to be leaner, inadequate adjustment for smoking would lead to underestimations of the risk ratios associated with the overweight and obese categories of BMI among non-smokers.
[31] This study concluded that, for non-Hispanic white adults who have never smoked, the BMI range of 20.0 to 24.9 was associated with the lowest mortality rates.
[34] The obesity paradox may therefore result from people becoming lean due to smoking, sedentary lifestyles, and unhealthy diets – all factors which also negatively impact health.
In fact, the obese have shorter lifespans because they get cardiovascular disease at an early age and have to live a longer proportion of their life with it.