Why Severe Obesity Is Not a Laughing Matter

Regular readers know that I look at BMI as a rather crappy measure of health – indeed there is very little relationship between mortality and BMI across a wide range of BMI levels.

However, once we approach severe obesity (the most rapidly rising subset of obesity in the population), there is very little doubt that carrying all that extra weight is associated with a substantially increased risk for illness and death.

Just how severely severe obesity affects life expectancy becomes clear from a new analysis by Cari Kitahara and colleagues from the US National Cancer Institute, published in PLOS Medicine.

For their analysis they pooled data from 20 prospective studies from the United States, Sweden, and Australia, sex- and age-adjusted total and cause-specific mortality rates (deaths per 100,000 persons per year) were assessed for people classified as obese class III (BMI 40.0–59.9 kg/m2) compared with those classified as normal weight (BMI 18.5–24.9 kg/m2).

Class III obesity was strongly associated with an increased risk of death due to heart disease, cancer, diabetes, nephritis/nephrotic syndrome/nephrosis, chronic lower respiratory disease, and influenza/pneumonia.

Overall, compared to people with a normal-weight BMI, a BMI of 40–44.9, 45–49.9, 50–54.9, and 55–59.9 kg/m2 was associated with an estimated 6.5, 8.9, 9.8, and 13.7 years of life lost – a substantial amount by any standard.

So, while experts and others may quibble over the value of BMI as a measure of health, there should be little doubt that severe obesity in the BMI 40+ range is associated with a substantial reduction in life expectancy.

All the more reason to increase efforts to better prevent and provide appropriated treatments to people who need them.

@DrSharma
Kananaskis, AB

Kitahara CM, Flint AJ, Berrington de Gonzalez A, Bernstein L, Brotzman M, MacInnis RJ, Moore SC, Robien K, Rosenberg PS, Singh PN, Weiderpass E, Adami HO, Anton-Culver H, Ballard-Barbash R, Buring JE, Freedman DM, Fraser GE, Beane Freeman LE, Gapstur SM, Gaziano JM, Giles GG, Håkansson N, Hoppin JA, Hu FB, Koenig K, Linet MS, Park Y, Patel AV, Purdue MP, Schairer C, Sesso HD, Visvanathan K, White E, Wolk A, Zeleniuch-Jacquotte A, & Hartge P (2014). Association between Class III Obesity (BMI of 40-59 kg/m2) and Mortality: A Pooled Analysis of 20 Prospective Studies. PLoS medicine, 11 (7) PMID: 25003901