Some medical studies have shown that obese patients appear to suffer less detrimental health consequences than those of normal weight. This apparent paradox contradicts traditional medical doctrine relating obesity with increased risk of numerous illnesses including heart disease, diabetes, and cancer. A recent study performed by Northwestern University scientists and published in the Journal of American Medical Association (JAMA) refutes the “obesity paradox.”

In 2013, a major study published in JAMA fueled the obesity paradox. Scientists from the Center for Disease Control and Prevention found that mildly obese patients had a 5% lower mortality than normal patients. They claimed that only moderately or severely obese patients suffered from earlier deaths than those of normal weight. Critics of the study argued that the conclusions were flawed because some “normal” patients in the study were formally overweight patients who had lost weight due to illness. A similar “paradox” was exploited by the tobacco industry to downplay the dangers of cigarette smoking. They cited studies that showed smokers and non-smokers had similar life expectancies but failed to exclude former smokers who stopped due to serious illnesses and impending death. In both scenarios, the results left the public and medical providers confused.

The current Northwestern scientists found a major flaw in the 2013 study. In their study published on February 28, they noted that obese patients did not live longer, but were diagnosed with heart disease at an earlier age. It may be true that obese patients with heart disease may have 5% lower mortality than their normal weight counterparts, but are generally younger to begin with. For example, an obese patient may be diagnosed with heart disease at the age of 50, while a normal weight individual will not be diagnosed until the age of 60. The 50-year-old obese patient may die from a heart attack 15 years later while the thin 60-year-old may die in 10 years, classifying the obese patient with a better survival rate (15 years versus 10 years). But in reality, the thin patient lived a longer life, 70 years versus 65 years.

The Northwestern University data concluded that obese male patients experienced 67% higher rate of cardiovascular disease than normal-weight men while living 1.9 years less. Obese women suffered even worse fate, with an 85% higher cardiovascular disease rate and 3.4 years of shortened lifespan than their normal weight counterpart. In short, obesity kills and the “obesity paradox” is a myth.