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Your BMI Suggests You Are Underweight

BMI result: below 18.5

En español |Your body mass index (BMI) suggests that you are underweight. Reaching and maintaining an appropriate weight can help you fight illness and enjoy overall good health.

See also: What's a BMI?

Low weight can stem from many factors, ranging from genetics to health conditions including depression, anxiety or eating disorders such as anorexia nervosa.


Your BMI is an estimate of your body fat based on your weight and height.

Also, treatment for certain illnesses can suppress the appetite, resulting in excessive weight loss

As you review your results keep in mind that BMI has its limits. For instance, BMI can underestimate body fat in frail, older people who have lost muscle mass.

You also should review BMI results in light of your gender, because the recommended amount of body fat differs for men and women.

For women, a BMI showing body fat of 20 percent to 21 percent is considered ideal. (The average American woman has about 22 percent to 25 percent body fat.) For men, the recommended amount of body fat is between 13 percent and 17 percent. (The average American man has approximately 17 percent to 19 percent body fat.)

One way to determine your desirable body weight is to use the following formula:

  • Women: 100 pounds pf body weight for the first five feet of height plus five pounds for each additional inch.

  • Men: 106 pounds of body weight for the first five feet of height plus six pounds for each additional inch.

But if you have a small body frame, you should subtract 10 percent from that number. For a large frame, 10 percent should be added.

If it’s advisable to gain weight, consult a dietitian, doctor or other health care provider. 

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