Your BMI Might Make You Think You’re Healthier Than You Are

Your BMI Might Make You Think You’re Healthier Than You Are

Your BMI, or Body Mass Index, gives you a number designed to indicate whether you are at a healthy weight or not. But as we’ve pointed out before, it isn’t always a reliable measure.

Photo by Jaimie Duplass (Shutterstock)

According to the health experts over at, BMIs tend to provide you with a more flattering look at your situation than reality might otherwise indicate.

BMI (Body Mass Index) is not a highly accurate measure of obesity. That being said, it’s more [flattering] than anything. BMI has a high rate of false negatives (obese people actually being classified as normal or overweight) encroaching on 50% in some studies, particularly among females. The amount of false positives seen with BMI (non-obese persons with enough lean mass to be classified as obese) is surprisingly small; less than 5% in men and 1% in women according to one study.

For those unfamiliar, you calculate your BMI by dividing your weight in kilograms by your height in metres squared. (If you don’t want to do this calculation yourself, just use an online BMI calculator like this one.) False positives likely occur more often in men due to heavier amounts of muscle mass, but regardless 5 per cent is still a very small number. Around 50 per cent, however, is a bit troubling.

If you find yourself on the higher end of the BMI range, don’t take comfort in such a rating. You might not be quite as healthy as you think, so see a doctor to find out if you need an adjustment in the level of your physical activity and your diet.

How valid is BMI as a measure of health and obesity? []


  • I find it fascinating that a measurement specifically and only designed for population studies (of sedentary individuals), has become a tool for individual grading and classification.

    The more articles like this pointing out the unreliability of the measure in individual (N=1) applications, the better.

  • According to MY BMI I am obese. I can see obliques and the top 4 abs but am bulking… Damn me why am I so fat!!! I’m gonna eat some cake and cry myself to sleep

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