Obese People Live Longer?
Interdisciplinary Research team led by professors of medicine and statistics makes headlines

The overweight normally go on diets to lose weight and live healthier. However, recent research showed the opposite result and made headlines. Previous research in the academia calls this phenomenon the ‘obesity paradox’.

Professor Sin Gon Kim’s research team (Division of Endocrinology and Metabolism, Department of Internal Medicine) along with research teams led by Professor Yousung Park (Department of Statistics) and Professor Juneyoung Lee (Department of Biostatistics) worked together to analyze the association between body mass index and risk of mortality. Their research cohort was one million people aged 30 and older who were all members of the National Health Insurance Service (NHIS).

Their research confirming the obesity paradox was published in PLOS one, an international medical journal issued by the Public Library of Science in the U.S.

The Korea University research team demonstrated that although obesity may cause diabetes, hypertension and many other diseases, people with such diseases become more cautious of their health. They are thus more likely to get frequent medical checkups, receive early treatments and regularly take better medicine, all of which eventually lowers their hazard ratio. Moreover, the research team argued that people who have low body weight tend to lack balanced nutrition and as a result become more vulnerable to immunological diseases.

Professor Kim said, “It is true that obese people are likely to suffer from diabetes, hypertension, hyperlipidemia, atherosclerotic cardiovascular diseases, and strokes. People may think that these chronic diseases accelerate mortality. However, people with such diseases are well aware of their health condition, which leads them to get early treatment and better medicine, which actually lowers the hazard ratio.”

The hazard ratio according to the Body Max Index (BMI) shows a drastic difference with regards to age. The research team stratified the population into three age groups, (30-49, 50-69, and over 70). When examining the 30-49 group, research showed that the hazard ratio of the low weight group (BMI<18.5) was 1.38 and the severe obesity group (BMI 30-32.4) was 1.39, basically showing no difference.

On the contrary, data showed that those over 50 with a low BMI registered a hazard ratio almost 3 times higher than those who were overweight. The severe obesity group (BMI 30-32.4) had a hazard ratio 1.2 times higher than the overweight group and the group consisting of people 70 and older was 0.81 times lower in the hazard ratio, showing significant differences.

Professor Kim said, “The reason why the obesity paradox is profoundly found in the elder group was due to their greater amount of muscles and fat protecting them from chronic diseases. For the elderly, health means physical strength. A moderate weight reflects a stable and balanced nutrition and healthy musculature. Therefore, it is important for the middle-aged and the older to maintain their weight to keep themselves fit and healthy.”

There is a higher chance for low weight people to have an imbalanced nutrition intake. This causes the immune system to collapse, resulting in increased exposure to pneumonia, tuberculosis and shingles, which slows down recovery. In particular, a lack of body fat and muscle leads to decreased bone density, increasing the possibility of developing osteoporosis.

Professor Kim stated, “As shown in the research, severe obesity and low weight can both accelerate the risk of mortality, and this was shown especially in the low weight group that had a BMI less than 18.5 and that showed high risk mortality in cardiovascular diseases and cancer. An adequate amount of fat helps us to build healthy immune cells that can promote body strength to protect us from external aggressors. We need to concentrate on not only absorbing appropriate amounts of nutrition, but also exercising for 10-15 minutes per day on a regular basis to promote flexibility and muscles.”