Life Cut Short by Obesity

When someone is too heavy, everyone knows that this is associated with numerous health risks.  A recent estimate on the amount of life lost due to obesity has been published (Obesity 2013; 21: 405-12).

Using data from the National Health and Nutrition Examination Survey (NHANES) I (1971-75), II (1976-80), and III (1988-94), the author was able to follow-up for 15 years and prospectively analyzed the data to calculate the relative risk of death and the “advancement period” of death due to obesity.  Stratification of death was adjusted for covariates including pre-existing illness, smoking, and older age.

The study focused on otherwise healthy nonsmokers to isolate the effects of obesity on mortality.  The averages of the cohorts was 46-48 years of age. While the author studied only 37,632 patients who had 8,791 deaths during the study, these results are relevant to about one-third of American adults.

Key finding: Compared to reference weight (BMI 23-25 kg/meter-squared), mortality was likely to occur 9.44 years earlier for those who were obese (BMI ≥ 30).

When the data was divided by weight, overweight (BMI 25-30 kg/meter-squared), mild obesity (BMI 30-35 kg/meter-squared), and obesity grades 2-3 (BMI >35 kg/meter-squared), the results were 4.40 years, 6.69 years, and 14.16 years respectively. The effect on advancement period mortality was less in older age groups (>55 years).

The main limitation of the study was its reliance on statistical analysis.  For those without a statistical background, Figure 2 which describes the mortality risk advancement period formula could as easily be written in Chinese.  Nevertheless, in the discussion the author underscores that these estimates are consistent with prior studies.

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