Obesity Paradox Does Exist

Adipose tissue has been shown to be a pivotal organ in the aging process and in the determination of life span. Owing to the rising prevalence of obesity, especially at younger ages, a potential decline in life expectancy is expected in the U.S. in the 21st century. Obesity, and mainly its abdominal form, is considered a major risk factor not only for type 2 diabetes, lipid disorders, and hypertension but also for coronary heart disease and certain cancers. In epidemiological studies, BMI, an indicator of relative weight for height (weight in kilograms divided by the square of height in meters) is frequently used as a surrogate for assessment of excess body fat. For characterization of the relative risks (RRs) of mortality and morbidity, the rates in underweight (BMI ,18.5 kg/m), overweight (25 to ,30 kg/m), class I obesity (30 to,35 kg/m), class II obesity (35 to ,40 kg/m), and class III obesity (BMI .40 kg/m) are compared with those in normal-weight subjects (18.5 to ,25 kg/m). A plot of the RRofmortality against BMI follows a U-shaped, or J-shaped, curve with the minimum mortality close to a BMI of 25 kg/m. Mortality increases as BMI increases above 25 kg/m and as BMI decreases below 25 kg/m (1). During the past decade, there is increasing evidence that patients, especially elderly, with several chronic diseases and elevated BMI may demonstrate lower all-cause and cardiovascular mortality compared with patients of normal weight. This article summarizes some of these paradoxical findings known as the “obesity paradox” and discusses potential causes of its manifestation.