Original Article Underweight, overweight and obesity

The purpose of this study was to determine the risk of all-cause mortality in the Canadian population across the new WHO/NIH BMI categories for the classification of overweight and obesity. The sample includes 10,725 adult participants (20–69 years) in the 1981 Canada Fitness Survey. A total of 593 deaths occurred during 13 years of follow-up. Hazard ratios (HR) for mortality were estimated using Cox proportional hazards models. Compared to normal weight individuals, there is an increased risk of mortality in the underweight category (HR 1.63, 95% CI 0.93–2.85) in addition to increasing levels of risk across the overweight (HR 1.16, 95% CI 0.96–1.39), obese class I (HR 1.25, 95% CI 0.96–1.65) and obese class II and III (HR 2.96, 95% CI 1.39–6.29) categories. Similar patterns were observed in sex-specific analyses. Underweight, overweight and obese Canadians are all at increased risk of mortality compared to those who are normal weight.