The health status of obese individuals in Canada

To determine whether there is a clinically relevant difference in the health state utilities of obese and non-obese individuals as measured by the Health Utility Index Mark III.

Secondary analysis of the population-based, cross-sectional, interviewer-administered National Population Health Survey (NPHS), 1996-1997. A probability sample of house-dwelling Canadians, excluding populations on First Nations Reserves, Canadian Armed Forces Bases, the Yukon and Northwest Territories, and long-term residents of hospitals or residential care facilities. The sub-sample used in this analysis consisted of 38 151 respondents (52.4% male) between the ages of 20 and 64 y, excluding pregnant women. Health Utilities Index-Mark III (HUI3) scores were used to define normal weight (body mass index (BMI) 19-24.9 kg/m(2)), overweight (BMI 25-29.9 kg/m(2)), obese (BMI 30-34.9 kg/m(2)), and morbidly obese (BMI> or =35 kg/m(2)) individuals. HUI3 scores were age- and gender-standardized.

The overall prevalence of obesity (BMI> or =30 kg/m(2)) in this Canadian population was 13.3%. The average difference in HUI3 scores between normal weight and morbidly obese respondents was 0.04 (P<0.001). Statistically significant (P<0.05) differences across BMI categories were found in each of the eight component attributes of the HUI3. The attributes with the most substantial difference between normal and obese patients were cognition, mobility and pain. All demonstrated a > or =2-fold increase in the proportion of individuals in poorer classifications of health when normal weight respondents were compared with the morbidly obese. The magnitude of the decrement in utility ratings associated with obesity was comparable with other chronic non-cardiovascular conditions such as migraine or colitis.

The results indicate that changes in self-rated health status appear to be due to significant changes across several relevant domain attributes. Obesity has a significant impact on both quality of life and health.