It's a common problem for women over age 65 and people who are sedentary. Doctors at the Mayo Clinic say the problem is that we have been defining obesity according to body mass index.

But body mass index measures lean mass or muscle and also fat. Therefore, somebody might have very little muscle mass and a lot of fat and still have a normal weight.

Doctors also say if your fat composition is over 25% for men and 35% for women, you are at increased risk of the same conditions as obviously overweight people: heart disease, diabetes, high cholesterol and high blood pressure.

Doctors recommend talking to your doctor about having your body fat percentage measured. Also, many health clubs have ways to measure body fat. These measurements can tell you if you should work on building lean mass and decreasing fat.

For more information, visit the Mayo Clinic's website www.mayoclinic.org/medical-edge