Body Mass Index or BMI has been around for over 180 years but is it an accurate measure of health? Invented in the 1830s, the measure is limited in its ability to tell a doctor and patient the full story around the health of a person. Instead, it is more of a good starting place.
Body mass index (BMI) is a measure of body fat based on height and weight that applies to adult men and women.
The measure itself provides no allowance for proportions of bone, muscle and fat of the individual. Simply, it doesn’t distinguish between body fat and lean body mass. BMI is also not as accurate a predictor of body fat in the elderly as it is in younger and middle-aged adults. Further, athletes and fit, health-conscious people who work out on a consistent basis can find themselves classified as overweight or even obese.
“A person’s percentage of body fat can also increase as they get older, whereas muscle mass typically decreases,” according to Edmund Pezalla, M.D., M.P.H., vice president and national medical director of Pharmaceutical Policy and Strategy at Aetna. “A person’s weight and height may not reveal those changes in body fat or muscle mass, either.”
Athletes and fit, health-conscious people who work out on a consistent basis can find themselves classified as overweight or even obese.
Recent research even suggests that with the use of BMI 34.4 million Americans considered overweight are actually healthy, including 19.8 million who are classified as obese. The research also found that more than 30 percent of Americans with BMIs classified as normal – nearly 21 million people – are actually unhealthy based on other diagnostic markers.
Looking past the limitations of BMI, more than one-third of Americans or nearly 80 million people are considered obese, according to the Centers for Disease Control and Prevention.
“The U.S. has an obesity problem,” Pezalla said, noting that doctors today are inclined to use BMI as “first stop” to assess risk for certain diseases, such as heart disease, high blood pressure, type 2 diabetes, gallstones, breathing problems and certain cancers.
Around the world, obesity costs $2 trillion a year in health care costs, lost productivity and investments made to mitigate its impact, according to the McKinsey Global Institute.
“BMI is a good initial measure of where someone may be in the care they may need,” Pezalla said. “Each person and their body are different, so their care should reflect that. However, because BMI doesn’t measure body fat directly, it isn’t a complete diagnostic tool. The measure should be used as a screening tool to identify potential weight and health issues, to be used in conjunction with other tests and measurements.”
BMI isn’t the only measure
Researchers argue that there are more accurate markers of health including physical activity, cardio-respiratory fitness, waist circumference, body fat percentage and/or a combination of them. Metabolic syndrome can be a much more complete way of assessing someone’s health. Metabolic syndrome, not a disease itself, is the name for a group of risk factors that can raise someone’s risk for heart disease and other health problems, including diabetes and stroke.
A doctor can diagnose metabolic syndrome based on the results of a physical exam and blood tests. A person must have at least three of the five metabolic risk factors to be diagnosed with metabolic syndrome. Metabolic syndrome can affect anyone at any age, but is most frequently seen in those who are inactive and overweight, with the majority of the excess fat in their abdominal area.
Metabolic syndrome is a cluster of conditions – increased blood pressure, high blood sugar, excess body fat around the waist and abnormal cholesterol or triglyceride levels.
“Metabolic syndrome can be controlled, largely with changes to someone’s lifestyle, including exercise and healthy eating habits,” Pezalla said. “The root cause of most cases can be traced back to poor eating habits and a sedentary lifestyle. If left untreated, complications from diseases associated with untreated metabolic syndrome can develop in as few as 15 years.”
Instead of BMI, think positive, healthy interventions
Recent research argues that the most effective health interventions are ones that emphasize healthy behaviors, provide practical skills and foster improved visions of ourselves. Targeting weight and weight loss in isolation of other health factors is less effective and sustainable for overall health improvements.
“By not focusing excessively on someone’s weight, you’re able to avoid any harmful outcomes or consequences that may have for the health and well-being of the patient, such as negative self-image,” said Pezalla.
“Overemphasizing weight can be discouraging for any individual who struggles with a number of health conditions that, frankly, may be more harmful. As physicians, we want to foster a positive environment to help get people on the right track to a happier and healthier life. Every individual has their own definition of optimal health.”