“There’s a thin man inside every fat man.” ~ George Orwell

You have, no doubt, heard about Body Mass Index (BMI).

Modern medicine uses BMI to determine if you are overweight or obese. If your BMI number is between 25 and 29.9, you are considered overweight. If it is 30 or above you are considered obese.

The problem is that most of the time you will hear these numbers used as if they were absolute. But they are not.

BMI is determined by comparing your height and weight. Ready? The formula is BMI = ( Weight in Pounds / ( Height in inches x Height in inches ) ) x 703.

Not being terribly math-centric, I don’t quite understand how they came up with this. Fortunately, if you want to know your BMI, you don’t have to do the math. There are any number of online calculators that will do it for you. Some will include other measurements. Probably the best two are here and here.

The reason BMI is used is that obesity raises the chance of someone getting obesity-related disease. These include:

  • Heart disease
  • Cancer
  • Diabetes

But can you rely on BMI to tell you these things? Not always.

For example, BMI may overestimate body fat in athletes and muscular people. Arnold Schwarzenegger’s BMI must be very high, but he is not overweight.

Also, in older people, BMI may underestimate body fat. This is true if they have lost muscle. So the amount of muscle you have makes a major difference one way or the other.

In addition, you can’t just use BMI to figure your risk. Waist size also counts. For women, the problem shows up above a 35 inch waist. In men it is above 40 inches. The two calculators linked above include this measurement.

You should also consider other factors:

  • Activity level
  • Food choices
  • Stress level
  • Family history

Is BMI just BS? Not exactly. But you shouldn’t rely solely on it to determine your risk for health problems.

All the best to you for your health and happiness,

Dr. Bruce Eichelberger

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