The relationship of excess body weight and health-related quality of life: evidence from a population study in Taiwan

Objective: Excess body weight is related to significant morbidity and mortality. However, less is known about the relationship of body weight to health-related quality of life (HRQOL), especially for Asian populations. We examined the relationship of excess weight and HRQOL in a general population sample from Taiwan. Research methods and procedures: This cross-sectional study used a national representative sample (n=14221) from the 2001 Taiwan National Health Interview Survey. Body weight was categorized using body mass index (BMI in kg/m(2)) as normal (18.5-24.9), overweight (25-29.9), and obese (>= 30). HRQOL was measured using the Taiwan version of the SF-36. We compared the body weight-HRQOL relationships by age, gender, and status of chronic condition, respectively. We especially used the Generalized Estimating Equations (GEE) to examine the relationships of BMI and HRQOL by taking into account the correlations of HRQOL within households. Four models were developed to adjust sequentially for sets of covariates: Model 1 with no adjustment; Model 2 adjusting for sociodemographic variables; Model 3 adding chronic conditions; Model 4 further adding smoking status. Results: Unadjusted physical HRQOL was best for normal weight, worse for overweight, and worst for obese individuals. For unadjusted mental HRQOL, overweight subjects had at least as good mental domain scores of HRQOL as those with normal weight or obesity, depending on the subscales. As age increased, excess weight was associated with worse physical, but not mental HRQOL. Compared to men, women with excess weight showed a greater deficit in physical HRQOL. Multivariable analyses suggested that obesity was associated with worse physical HRQOL compared to overweight, which, in turn, was worse or comparable to normal weight. Specifically, in the model adjusting for demographic variables, the deficit in physical functioning and physical component scores for the obese vs normal weight were statistical significant (P < 0.05) and clinically important difference (effect size >= 0.3). Both obesity and overweight were associated with higher mental component scores than normal weight, but the effect size was < 0.3. Conclusion: In Taiwan, excess weight was related to worse physical, but not mental HRQOL. The lack of impact of increased body weight on mental health status presents a potential challenge to preventing the increases in obesity. More research is needed to elucidate the mechanisms by which excess weight affects specific domains of HRQOL, and to develop effective prevention strategies.