Q: I would like to know how relevant the BMI is when it comes to muscle mass. Isn't it true that muscle weighs more than fat? For instance, when I was in high school, my weight was 140 pounds during a weigh in. The girl in line behind me, who was visibly heavier than me by all accounts (I definitely looked slimmer) weighed in at 117 pounds. Today, I don't care as much about the numbers on the scale but at the time I was a bit traumatized! People routinely under-guess my weight by at least twenty pounds. I am definitely not making excuses, but I wonder where we draw the line between being truly "overweight" versus not measuring up to what may be an outdated standard.
Dr. Kasongo: We tend to be very obsessed by our weight and scales and while this may help you keep track of wieght gain or loss, it isn't telling you how healthy you are. Because the truth is that some people think they are overweight, when the amount of fat they have on their bodies is just fine, while others may carry hidden fat that the scale won't tell them about. Our bodies are made up of a lot of different kinds of tissues (plus a lot of water). There is muscle, fat, bone, and specialized tissue such as is in our various organs. The body fat percentage is just that –- the percentage of our weight which is made up of fat. Body fat percentage is similar to terms such as body fat ratio and body composition. It is important not to confuse BMI with body fat percentage. I get really irritated when official websites confuse the two. BMI (body mass index) is a formula based on height and weight. It was developed because in the general population, it is correlated with body fat. Women with a BMI of 25 to 29.9 are considered overweight, while women with a BMI of 30 or more are considered obese. All adults (aged 18 years or older) who have a BMI of 25 or more are considered at risk for early death and disability from being overweight or obese. These health risks increase as the BMI rises. And yes, there are danger zones for fat storage For most women, carrying extra weight around their waists or middle (with a waist larger than 35 inches) raises health risks more than carrying extra weight around their hips or thighs. These health risks include heart disease, diabetes, and cancer.
Mana Kasongo, MD is a board-certified emergency physician as well as a nationally published writer with expertise in emergency health care issues and women's health. Email her at firstname.lastname@example.org with your women's health questions. All correspondence will be kept strictly confidential and your name will not be used if your question is selected. The Ask Dr. Kasongo column is for entertainment purposes only and the recommendations are merely suggestions. If you have a true concern you should consult your personal physician.