OBJECTIVES: A higher Body Mass Index (BMI) is associated with decreased quality of life (QoL). Additional athropometric measurements like waist circumference (WC) may define obesity and explain its health consequences. The objective of this study was to determine if utility (EQ5Dindex) varied by BMI category, as WC varied. METHODS This retrospective study used the latest data from the England Health Survey (2003). A general linear model (GLM) was developed that included factors associated with utility, standardising for age and sex to generate estimates of utility with relation to obesity (obesity categories: normal [Nl, BMI 18.5–24.9 kg/m2], overweight [Ov, 25.0-29.9 kg/m2], obese [Ob, = 30 kg/m2], and thirtiles of WC, L=low, M=medium, and H=high). RESULTS The standardised mean utility by BMI category for men was: Nl=0.877, Ov=0.894, Ob=0.858. Standardised mean utility by BMI category for women was: Nl=0.879, Ov=0.871, Ob=0.812. Standardised mean utility by WC category for men was: L=0.887, M=0.877, H=0.866. Standardised mean utility by WC category for women was: L=0.872, M=0.857, H=0.833. BMI and WC were dependent and interacting determinants of utility. For females in the nine obesity groups, the standardised mean utility was as follows: Nl/L=0.878, Nl/M=0.877, Nl/H=0.882, Ov/L=0.896, Ov/M=0.873, Ov/H=0.844, Ob/L=0.842, Ob/M=0.822, Ob/H=0.774. For men: Nl/L=0.862, Nl/M=0.882, Nl/H=0.888, Ov/L=0.907, Ov/M=0.893, Ov/H=0.883, Ob/L=0.892, Ob/M=0.856, Ob/H=0.828. CONCLUSIONS In both women and men, the highest EQ5Dindex values (best QoL) was evident in overweight people with a low WC. A reduction in WC in obese people resulted in a greater gain in utility than the same change in normal or overweight people. Use of both BMI and WC, rather than a single measure of obesity, provided a more precise prediction of health-related utility. Utility varied more widely as a function of waist circumference in higher BMI categories.