Understanding BMI: What Body Weight Is Right for You?

Your Body Weight Is More than a Number on a Scale

By Michael Ormsbee, Ph.D., Florida State University

If you’re tracking your progress in a fitness or diet plan or just want an accurate assessment of your overall health, you will probably look at your weight. However, body weight does not always paint a clear picture of your health. Discover why BMI is a superior method of weight management, though it still has its shortcomings.

Scale and measuring tape on bathroom floor.
The success of a weight-loss plan through diet and exercise is better attained by measuring BMI, not weight on a scale. Photo by New Africa / Shutterestock

Is Body Weight the Best Indication of Health?

Over the past 25 years, the body weight that Americans consider ideal has steadily increased by over 10 pounds. Today, the average woman weighs 157 pounds but would like to weigh 140 pounds, while the average man weighs 193 pounds but would ideally weigh about 185 pounds.

The trouble is, body weight gives us no indication of how much fat or muscle a person carries on their frame. This relative proportion is critical as it’s related to our overall health, how our body moves and behaves, and how we look and feel.

Extreme weight loss shows on TV feature men and women losing weight drastically in just a few weeks. While the hosts tout any weight loss as a success, they rarely differentiate between fat loss and muscle loss.

But no one ever quantifies those losses. Do they lose fat? Or do they lose muscle, too? For some people, tracking body weight is an appropriate tool to keep them on track with their goals, but for others it may be misleading.

When the Scale Doesn’t Tell the Whole Story

According to Dr. Michael Ormsbee, Associate Professor in the Department of Nutrition, Food, and Exercise Sciences at Florida State University, in his programs, he not only tracks body weight, but also muscle mass and fat mass changes. These are tracked before, during, and after an exercise and nutritional intervention of several weeks or months.

“One of the most glaring examples of weighing misuse was when a participant—an overweight, middle-aged woman—came to me and told me she was going to drop out of the program because she was having no results,” Dr. Ormsbee said. “This was a total shock because I had personally measured her success in the study. She had improved her upper and lower body strength and had increased her ability to complete high-intensity cardiovascular exercise.”

Additionally, the woman told him that she was feeling better than she had in the past 10 years. She had steadily lost fat mass and gained muscle during her first six weeks of the program.

She was an absolute image of success. But what did her scale read? Failure.

The woman in Dr. Ormsbee’s program lost several pounds of body fat, which was replaced by a similar weight in muscle. Her body composition changed for the better, her clothes fit better, and she received compliments from friends and family, but she didn’t care. To her, a steady number on the scale meant failure.

BMI: A Better Way to Measure Body Composition

How, then, can we better quantify success with weight management?

One way is through body mass index (BMI). BMI compares your body weight in kilograms to your height in meters squared. There are four main categories of BMI:

  • Underweight: less than 18.5
  • Normal weight: 18.5 to 24.9
  • Overweight: 25 to 29
  • Obese: over 30

Research has consistently shown a positive association between a high BMI and a greater risk of cardiovascular, pulmonary, and metabolic disease. If you are curious about your own body mass index, calculate it.

However, BMI is only useful in certain situations. It’s most effective for averaging large sample populations, like a state or country—or in clinical situations to quantify health risks for a patient who is overweight and overfat at the same time. Sometimes it can be less effective as data when measuring certain individuals.

For example, if two people are the same height and the second person weighs a bit more, they will have a slightly higher BMI. Since BMI assumes any extra weight is due to greater fat weight, it will assume the second person is more at-risk for health problems. It does not account for the proportion of muscle mass or fat mass, which is the composition of your body weight.

Another example is a typical NFL running back. Professional football players are very strong, with lots of lean muscle mass and very little body fat. A running back who stands six feet tall and weighs about 230 pounds would have a BMI over 31 kg/m2. That falls into the “obese” category, though, he clearly isn’t.

Similarly, the BMI for the average U.S. woman—5′6″ tall and 156 pounds—is 25.2, which is considered overweight.

Therefore, when it comes to assessing your health, measures like BMI or body weight should be taken with a grain of salt.

This article was edited by Kate Findley, Writer for Wondrium Daily, and proofread by Angela Shoemaker, Proofreader and Copy Editor for Wondrium Daily.
Dr. Ormsbee is an Associate Professor in the Department of Nutrition, Food, and Exercise Sciences and Interim Director of the Institute of Sports Sciences and Medicine in the College of Human Sciences at Florida State University.

Michael Ormsbee is an Associate Professor in the Department of Nutrition, Food, and Exercise Sciences and Interim Director of the Institute of Sports Sciences and Medicine in the College of Human Sciences at Florida State University. He received his MS in Exercise Physiology from South Dakota State University and his PhD in Bioenergetics from East Carolina University.