Waist...

 As we get older, the excess weight could increase the risk of developing diseases, such as diabetes, high blood pressure, dementia and even cancer.

In women, a single increase in skirt size between mid-20s and mid-50s could make them three times more likely to have breast cancer after menopause, according to WebMD.

The body mass index (BMI) uses height and weight to measure body fat. However, for older adults, BMI in some cases can understate body fat.

This leads us to properly considering waist size. 

If the waist size appears more than 35 inches for a woman or 40 inches for a man, a person can be considered obese, according to Rush University Medical Center.   

Even those who are already in their 80s can still develop lean muscle mass and keep body fat down through exercise and healthy diet.