Can someone with a healthy BMI be unhealthy?

Is your health goal to get thin or to get active? Science suggests it may be best to think more about breaking a sweat than about stepping on the scale.

In a recent study, being inactive translated into a higher risk of heart disease, regardless of a person's body mass index (BMI).

BMI is a measure of overall body weight that takes into consideration a person's height. Medical experts have used it as an indicator of body fatness and thus a tool for determining disease risk. But in a recent study, inactive people were in a higher heart-risk category no matter what their BMIs were. Seems their couch-potato ways translated into a disproportionately big waist, irrespective of how much -- or how little -- they tipped the scales. And a too-big waist means big trouble for the heart.

Having a BMI within a normal range is great, but it's not the be-all and end-all of good health. You can have a normal BMI and still be unhealthy -- especially if you don't exercise. In the recent study, inactive men had a higher risk of future heart disease compared with active men. Again, this was regardless of BMIs and bathroom scales. Inactive women fared even worse than men when it came to heart disease risk, and it's all because activity affects body proportion. Exercise makes it less likely that your body fat will get stored in the most dangerous place you can store it: around your abdomen.

Marjorie Nolan Cohn
Nutrition & Dietetics

Obesity is a state of excess adipose tissue mass, or body fat. This condition usually translates into excessive body weight. On the one hand obesity can develop even in the absence of excessive body weight, whereas on the other hand a person (e.g., a body builder) can develop remarkable overweight without excessive body fatness. Meaning, ‘slim’ people can have a high fat mass and ‘overweight’ people (for their height) can have low fat mass. 

For adults, overweight and obesity ranges are determined by using weight and height to calculate a number called the "body mass index" (BMI). BMI is used because, for most people, it correlates with their amount of body fat.

It is important to remember that although BMI correlates with the amount of body fat, BMI does not directly measure body fat. As a result, some people, such as athletes, may have a BMI that identifies them as overweight even though they do not have excess body fat.

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Important: This content reflects information from various individuals and organizations and may offer alternative or opposing points of view. It should not be used for medical advice, diagnosis or treatment. As always, you should consult with your healthcare provider about your specific health needs.