Do you have too much fat?

Excess fat is consistently associated with higher rates of disease and death in most populations. How do you know whether you have too much fat, and how much?

There are multiple ways to measure body fat, with different pros and cons. Remember that weight loss programs usually result in muscle loss as well as fat loss, so it can be helpful to use a metric more sophisticated than weight alone.

Body Mass Index

The most commonly used method of assessing obesity is the BMI, or body mass index. The body mass index is a simple formula, with a number calculated using your weight and height. It is widely used because it is easy to use. It is also fairly reliable in a majority of people.

As the internet is quick to point out, the BMI can be inaccurate in some people. Very muscular people such as athletes and bodybuilders can have a high BMI without being obese. What is much more common, however, is the opposite scenario. In people who have decreased lean muscle mass, the BMI may be normal or near normal despite a high body fat percentage. This is very common in the elderly, because muscle mass declines with age.

A BMI between 25 and 30 is considered overweight, and greater than 30 is considered obese, according to the NIH, in Caucasian, Hispanic, and black populations.  These cutoffs do not accurately reflect risk in Asians and South Asians, who have higher levels of risk with smaller amounts of excess fat.

Once again, reduction in BMI alone may not tell the whole story when you are trying to lose weight, since you may be losing muscle as well as fat. This is why body measurements can come in handy.

Waist Circumference

Another simple way to assess obesity is measuring waist circumference. This value is particularly helpful because we know that abdominal fat is associated with high blood pressure, unfavorable cholesterol profiles, diabetes, and heart disease. You can easily measure your waist circumference with a tape measure. Measure horizontally around your waist at the level of your upper hip bone (doctors call this the iliac crest). The measurement should be made after you exhale from a normal breath.

A waist circumference of greater than 40 inches in men or 35 inches in women is associated with increased risk.  Once again, lower cutoffs should be used for Asians.

Body fat percentage

Another way to quantitative obesity is body fat percentage.  This can be done through caliper measurements by a trained professional, but this is not commonly available. Similarly, imaging for obesity such as a DEXA scan or MRI is usually only done for research purposes. An easier method to determine body fat percentage is to use a calculator that incorporates body measurements. The United States Army and Navy Body Fat Calculators are useful tools to do this.  All you need is a tape measure! You can use them to discover your body fat percentage, and as a bonus, you can find out if you are eligible to join the armed forces!

US Army Body Fat Calculator

US Navy Body Fat Calculator

Another way to calculate body fat percentage is a specialized scale that can use electrical impedance to analyze body composition. These scales have electrodes on them and send a small amount of electricity through your body (not enough for you to feel). Based on the measured resistance of your body to the flow of electricity, these scales can estimate your body fat percentage.