Association between Body Mass Index and Health-Related Quality of Life: The "Obesity Paradox" in 21,218 Adults of the Chinese General Population

PLoS One. 2015 Jun 18;10(6):e0130613. doi: 10.1371/journal.pone.0130613. eCollection 2015.


Background: There was no consistent recognition of the association between high or low body mass index (BMI) and health related quality of life (HRQL). The aim of this research was to study the association between BMI and HRQL in Chinese adults, and to further explore the stability of that association in the subgroup analysis stratified by status of chronic conditions.

Methods: A total of 21,218 adults aged 18 and older were classified as underweight, normal weight, overweight, class I obese, and class II obese based on their BMI. HRQL was measured by the SF-36 Health Survey. The independent impact of each BMI category on HRQL was examined through standard least squares regression by comparing the difference of SF-36 scores and the minimum clinically important differences (MCID), which was defined as 3 points.

Results: Compared to the normal weight, the class I obese was significantly associated with better HRQL scores in the mental component summary (MCS) (75.1 vs. 73.4, P<0.001). The underweight had the lowest score in both the physical components summary (PCS) (75.4 vs. 77.5, P<0.001) and mental components summary (MCS) (71.8 vs. 73.4, P<0.001). For the MCID, the HRQL score was reduced by more than 3 points in the physical functioning for the class II obese (D=-3.43) and the general health for the underweight (D=-3.71). Stratified analyses showed a similar result in the health subjects and chronic conditions, and it was significant in the chronic conditions.

Conclusions: The class I obese showed the best HRQL, especially in the mental domain. The worst HRQL was found in the underweight. The class II obese reduced HRQL in the physical functioning only. "Obesity paradox" was more obvious in the participants with chronic conditions.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adolescent
  • Adult
  • Aged
  • Aged, 80 and over
  • Body Mass Index*
  • China / epidemiology
  • Female
  • Health Status
  • Health Surveys
  • Humans
  • Male
  • Middle Aged
  • Obesity / epidemiology*
  • Overweight / epidemiology
  • Quality of Life*
  • Thinness / epidemiology
  • Young Adult

Grant support

This work was supported by grants from the National Program on Key Basic Research Project of China (973 Program) (No. 2011CB505403;2005CB523501) and the National Natural Science Foundation of China (No. 30873256). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.