The Cost of Obesity to the Individual

Source: Tufts University
February 14, 2003

Despite warnings that obesity is causing a surge in diabetes, heart disease, and medical costs, waistlines continue to expand. To further quantify the danger of obesity and overweight, researchers from John Hopkins University and the University of Alabama estimated the number of years of life lost (YLL) due to obesity during an adult's life span.

Data analyses

Body mass index (BMI) data were collected from the Third National Health and Nutrition Examination Survey (NHANES III; 1988-1994). The authors derived the hazard ratio (HR) for death at any BMI level and age by combining data from the First National Health and Nutrition Epidemiologic Follow-up Study (NHEFS) and the NHANES II Mortality Study (NH2MS).

Statistics from the Center for Disease Control and Prevention were used to derive the probability of death during each year of life. Using these data, researchers calculated the YLL (the difference between the numbers of years of life expected if an individual is obese vs. not obese), based on age and BMI category compared to the reference BMI category of 24, which is the upper end of desirable weight.

Years of life lost

The YLL pattern among whites was a J- or U-shaped curve. For instance, those with low BMIs (<17 to 19) had 1 to 9 YLL and those with high BMIs (>/=35) had losses of 9 to 13 years. White men in their 20s with a BMI of >/= 45 had 13 YLL compared to those with a BMI of 24. A white woman of the same age and BMI category lost 8 years due to obesity.

Among blacks there was not a consistent reduction in life expectancy until BMIs of 37 for women and 32 for men were reached. At lower BMI levels, being overweight appeared to increase life expectancy. Having a BMI of >/= 45 at age 20 resulted in 20 YLL for black men and 5 YLL for black women.

The authors offer several possible explanations for the effect of race on YLL. First, BMI may have a differing effect on mortality depending on race. Second, exposure to other factors that affect mortality risk - socioeconomic and health status, age distribution, and other variables - may differ by race. Also, confounding factors, such as other illnesses, may not be distributed equally across races. And lastly, body composition, specifically central adiposity, may be more important than BMI in determining mortality and body composition in different races.

Impact on health

The authors of the accompanying editorial suggest that a concrete image such as 'years of life lost' may make it easier for physicians to communicate to their patients the ultimate cost of obesity. But, they say, this one end point obscures the fact that a lifetime of overweight reduces a person's quality of life and radically increases the risk of chronic disease, as even a moderately elevated BMI increases the risk of hypertension and type 2 diabetes, in both whites and blacks. They further point out that intentional weight loss can reduce the likelihood of developing these diseases, but potential confounders - such as pre-clinical disease - make it difficult to readily equate weight loss with lowered mortality risk.

Advice to patients

Obesity will continue to take a toll on people's health and quality of life, as well as on the healthcare system. Physicians need to make this message relevant to patients and offer direction as to how to achieve or maintain a healthful body weight.

Source

• Years of life lost due to obesity. KR. Fontaine, DT. Redden, C. Wang,  et al., JAMA, 2003, vol. 289, pp. 187--193

Related Links
Waist Circumference as a Measure For Health Risks
Excess Weight Adds Health Problems
Heart Failure Linked to Obesity
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