Jan 022013

The obesity paradox is a problematic statistically indication that slightly overweight people tend to live longer than people who weigh less than they do. This is a conclusion by a study published in the recent issue of JAMA (The Journal of the American Medical Association – January 2,2013).

This study compared people with various BMI’s or Body Mass Indexes. The study compared overweight BMI (25 to 30), grade 1 obesity BMI (30 to 35) and grades 2 and 3 obesity BMI (greater than 35) relative to the lower BMI level of 18.5 to 25.

According to the CDC (Centers for Disease Control and Prevention), BMI is “a number calculated from a person’s weight and height. BMI is a fairly reliable indicator of body fatness for most people. BMI does not measure body fat directly, but research has shown that BMI correlates to direct measures of body fat.”

However, two problems with associating your BMI with health is that BMI

  • Doesn’t differentiate between fat and muscle mass
  • And BMI doesn’t take into account where the fat tissue is located in your body.

For example, if you have more healthy muscle mass than normal, you can have a BMI that indicates being overweight. However, you can be healthier than the average population of people who weight less than you do. Or, if most of your fat tissue is located just below your skin in your thigh and butt areas, you can be healthier than lighter people who have mostly abdominal or belly fat, also called visceral fat.

Visceral or belly fat is associated with an increased risk of developing type 2 diabetes, heart disease and various cancers. Visceral fat tends to accumulate deep in your abdominal cavity and surrounds your vital organs. On the other hand, fat located just below your skin in other areas of your body has no association with developing life threatening diseases.

In addition to not knowing what type of fat that you have and where it is located, some people with healthy BMI’s may be thin due to a chronic and life threatening illness.

The specific conclusions of this new study show statistically that grades 2 and 3 obesity, which have BMI’s greater than 35, were associated with significantly higher all-cause mortality. In other words, people with BMI’s greater than 35 have a significantly higher chance of dying prematurely than those with BMI’s between 18.5 and 25.

The problem with the Obesity Paradox is that overweight people with BMI’s between 25 and 30 have a significantly lower mortality rate than those with the presumably healthier BMI’s between 18.5 and 25. But as mentioned earlier, you have to take into account how much muscle mass you have relative to fat tissue, where the fat tissue is located and what type of fat tissue you have, and why you may have a lower BMI.

People with a lot of muscle mass and very little visceral fat will tend to be healthier than someone who weighs less but has more visceral fat relative to their muscle mass. And some people who weigh less may be suffering from a severe and life threatening illness.

That is why people must be careful with the conclusions of this study. The authors stress that their conclusions do not mean that we should gain more weight. We should have the proper diet and exercise program that allows us to develop more muscle mass and burns away visceral or belly fat.

In conclusion, BMI is an inexpensive way to determine your general state of health. However, it needs to be used in conjunction with other factors, such as how much muscle mass do you have relative to fat tissue, and how much visceral fat that you have relative to other types of fat.


JAMA: Association of All-Cause Mortality With Overweight and Obesity Using Standard Body Mass Index Categories

CDC: About BMI For Adults