Since 1999, a phenomenon – obesity paradox – has been a subject of investigation. In general population, normally, over-weight and obesity is associated with risks of many diseases but in certain persons it is associated with a decreased mortality risk as compared with normal weight, which is termed obesity paradox. An obesity paradox has been reported both in cardiovascular and non-cardiovascular conditions.
Pre-obesity is defined as a body mass index (BMI) of 25.0 to 29.9. This BMI range also represents over-weight. A BMI of 30 & above represents obesity.
Another paradox is represented by many obese individuals, in whom the mortality risk associated with obesity is offset by exercise. So it appears that low cardiovascular fitness and physical inactivity are greater health threat than obesity.
It has been found that overweight patients with a BMI of 25.0 to 29.9, suffering from angina, heart attack or heart failure have a lower risk of dying from the disease. This pattern remained consistent across differences in age, sex and treatment methods. It has also been found that the under-weight patients who have been treated with percutaneous coronary interventions (PCI) have three times more risk of death than over-weight patients. Even after cardiac bye-pass surgery no increase in mortality is seen in over-weight or obese patients. It is difficult to explain this trend but it has been put forth that some unidentified mechanisms protect such patients of heart disease from premature death.
The so-called obesity paradox has also been observed in patients of diabetes, kidney failure and peripheral artery disease (PAD). It has been found that some over-weight and obese persons with diabetes tend to live longer than their normal weight peers. In spite of being over-weight and obese, they are metabolically healthy. These diabetics also have fewer complications of the disease. It is probable that the excessive weight is protective. At the same time, it has been observed that the diabetics with the normal weight have a higher mortality rate. This is also difficult to explain but it may be that such persons are genetically destined to develop diabetes and have higher mortality.
Since some over-weight persons with some chronic diseases have better survival rate than normal weight persons, it appears that losing weight might not be in the best interest of such persons. On the other hand, more emphasis should be laid on cardiovascular fitness and physical activity in over-weight and obese people.