Obesity Can Shorten A Person's Life By Years, Alarming New Study Shows, But It's Complicated

It seems intuitive (at least in American culture) that obesity isn't healthy, but no observation is too obvious to be worth confirming scientifically. And a study by epidemiologists at the McGill University Health Centre provides new evidence that obesity can shorten a person's life by years — eight, to be exact (or even more, depending on how you count obesity's effects).

In a collaborative effort including researchers from several Canadian universities, the epidemiologists developed a computer model to make sense of data on almost 4,000 Americans collected between 2003 and 2010. The data came from the National Health and Nutrition Examination Survey, an important source because it reflects information from both interviews and physical examinations (whereas merely self-reported data on weight would be much less reliable).

Their findings basically corroborate conventional thinking on excessive weight and its ill effects on health:

Individuals who were very obese could lose up to 8 years of life, obese individuals could lose up to 6 years, and those who were overweight could lose up to three years. In addition, healthy life-years lost were two to four times higher for overweight and obese individuals compared to those who had a healthy weight, defined as 18.5-25 body mass index (BMI). The age at which the excess weight accumulated was an important factor and the worst outcomes were in those who gained their weight at earlier ages.

In other words, the more excess weight you carry, the greater your risk of dying prematurely. Excess weight also threatens your number of healthy life-years (free of disease or disability), because the quality of your life matters in addition to the mere quantity. And the longer you spend carrying excess weight, the more likely you are to face subsequent, related health risks.

Admittedly, the relationship between weight and health is a complicated one. Overweight people may not be at risk of shortened life if they're "metabolically fit," but it may be more difficult to develop and maintain metabolic fitness in the first place. Some of the health harms of extra weight may actually be the harms of lowered social status in disguise, but that doesn't make them any less real. Although many obese people don't die early, we each have to consider the complicated empirical picture suggesting that carrying extra weight probably isn't a good idea, all things considered.