Original Article Underweight, overweight and obesity: relationships with mortality in the 13-year follow-up of the Canada Fitness Survey

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 under-weight category (HR 1.63 95% Cl 0.93-2.85) in addition to increasing levels of risk across the overweight (HR 1.16, 95% Cl 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% Cl 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. (C) 2001 Elsevier Science Inc. All rights reserved.