For years, doctors, nutritionists, and anyone with a calculator have been using a mathematical formula called Body Mass Index (BMI) to determine whether someone is overweight or not. BMI does a pretty good job of determining whether or not you’re obese, and since obesity is known to play a major role in one’s health and risk of premature death, everyone naturally assumed that BMI was also a pretty good predictor of mortality. Turns out it isn’t as accurate as we’d thought.
Dr. Raj Padwal at Canada’s University of Alberta analyzed data from 15,000 people with an average BMI of 36 or higher—people who were so severely obese that they were candidates for bariatric surgery. Padwal followed them for 10 years and compared BMI’s accuracy in predicting premature death with four other factors: Age, having type 2 diabetes, smoking habits, and sex (being male or female).
Here’s how it played out. For every point increase in BMI, the risk of death increased by 3%. The patient’s age increased the risk of death by 9%. Having diabetes increased that risk by 125%, smoking by 62%, and being male by 50%.
Bottom line: If your BMI says you’re obese and you’re considering bariatric surgery—or your medical provider says you’re a candidate—don’t base your decision solely on your BMI. Ask your provider to investigate the other factors as well.