Improving Fitness Is as Important as Reducing Fatness

Today is Part I of a 2-part discussion regarding the current science of obesity. In these 2 blogs, I’m posing the following question—“Is all obesity bad?”

What is BMI?

The body mass index (BMI) is a method for arriving at an educated guess about how much fat a person is carrying around. The BMI system does not actually measure the percentage of one’s body fat; instead, it bases its calculations on an individual's weight and height. That is, the BMI is defined as the individual's weight (body mass) divided by his or her height-squared. In metric terms, this looks like this: kg/m2—where the person’s weight is given in kilograms and the height in meters—but most BMI calculators will take pounds and inches just as easily.

If you know your height and weight, it’s easy to find an online calculator to determine your BMI. Here are some BMI calculators offered by the National Institutes of Health and the Centers for Disease Control and Prevention.

What is obesity?

In most cases, obesity is defined as a BMI equal to or greater than 30. Do you qualify as obese? If so, this discussion is for you.

In this entry, Part 1, I’m going to discuss the relative importance of improving one’s cardiorespiratory fitness—how much you can exercise—and reducing one’s fatness (shedding fat pounds).

Fitness and Fatness

Scientists have long debated the relative importance of being physically fit versus the benefits of a normal body weight (usually a BMI less than 25 kg/m2). Is it more important to be in good physical shape or to be slim and trim? These two standards of health are hard to separate. Commonly, heavier people can’t exercise as much and have lower fitness—but this is not always the case. Some heavy people are quite physically fit. On the flip side, some normal-weight people are very unfit.

A recent paper in the European Heart Journal sheds light on this question of the relative merits of fitness versus normal weight. This study revealed 2 important findings that every heavy person should be aware of:

  1. Obese people with good fitness have less cardiovascular risk factors (like hypertension and diabetes) compared to similarly obese people with poor fitness.
  2. Obese people who achieve fitness levels equal to their normal-weight counterparts have no increased risk of heart disease, cancer, or dying of any other cause!

Everybody, listen up—normal-weight people with poor fitness probably are worse off than heavy people with excellent fitness. What a humbling yet exiting finding!

Even if you can’t lose any weight, exercise!

The implications of this study are tremendous. As a doctor, I commonly have overweight and obese patients tell me that they stopped exercising because they can’t lose weight. But this is exactly the wrong thing to do. Even if you are not losing fat pounds, and even if your cholesterol is not budging, you are doing wonders for your cardiovascular system by exercising.

And for those of you who can never achieve a normal weight—that may be OK! If you can achieve an excellent fitness level equivalent to that of most normal-weight people, your prospects for good health are excellent.

In Part 2 of this series, I’ll pose another important question: Are some types of body fat worse than others?

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