America’s Obesity Epidemic: BMI in Context
This article is Part 1 in a 2-part series. Part 2 will focus on medications for weight loss and type 2 diabetes.
Obesity was first recognized as a disease by the World Health Organization (WHO) in 1948. It’s a complex, chronic condition that’s rooted in modern life itself—specifically, industrialized agriculture and changes in the way we eat, work, move and live.
So what, exactly, is obesity? The WHO defines it as abnormal or excessive fat accumulation that presents a risk to health. Until recently, it has tended to be diagnosed via a measure known as BMI, which stands for body mass index. A person’s BMI is based on their weight relative to their height.
But this January, the Lancet Commission on the Definition and Diagnostic Criteria of Ƶ Obesity recommended a new way of viewing BMI as just one among several ways to assess obesity.
Continue reading for answers to your FAQs around weight and obesity, and for help in making sense of the Lancet Commission’s new recommendation, thanks to Dr. Mohini Aras, an assistant professor and assistant attending physician at Ƶ who treats patients at the institution’s Comprehensive Weight Control Center.
What are the pros and cons of BMI as a measure of obesity?
“BMI is a tool that originally emerged from population studies,” Dr. Aras says, “and it ’t necessarily applicable to individual patients.” In other words, it’s a very rough measure of obesity that has several limitations.
For one, BMI does’t differentiate between lean muscle mass and fat. “It's actually the ratio of lean to fat that influences your future risk for developing cardiovascular disease,” Dr. Aras explains, including heart attack, stroke and and peripheral vascular disease, which affects the blood vessels in the arms or legs.
Even before any hint of heart disease, an unfavorable lean-to-fat ratio may raise your chances of developing:
- Diabetes, pre-diabetes or insulin resistance
- High cholesterol or high triglyceride levels
- High blood pressure
- Excess body weight itself
As well, BMI doe’t take fat distribution into account. Excess fat around the waist or belly increases cardiometabolic risk, she says.
The Lancet Commission recommends using BMI as a screening tool, and to confirm the diagnosis of obesity through measurement of body size.
“Using BMI as the only tool for diagnosing obesity may lead to overdiagnosis of obesity in people with a BMI that’s greater than 30, and its underdiagnosis in people with BMIs that usually classify them as overweight but not obese.”
What other methods do you use to diagnose obesity?
Body size and composition can be measured via the following:
- A DEXA scan, used to measure bone density and body composition, is the gold standard for assessing a patient’s fat vs. muscle ratio.
- BIA, or bioelectrical impedance analysis, employs a mild electrical current and measures resistance to it. Body fat is more resistant, while lean muscle mass is much less so. BIA is somewhat less reliable than DEXA, but it’s also less expensive.
- A waist circumference that’s equal to or greater than roughly 40 inches in men and 36 inches in women is yet another indicator of obesity.
- A waist-to-hip ratio of greater than 0.90 for men and 0.50 for women is also part of the mix, along with a waist-to-height ratio of greater than 0.50 for both men and women.
What is driving the obesity epidemic in America?
Many factors are at play, but the basic root of the problem, says Dr. Aras, is that our food environment has changed much faster than our genetics, which are designed to hold onto our fat stores to avoid famine.
How does obesity typically affect a person’s health?
Obesity affects many aspects of a person's physical and mental health. In addition to the cardiovascular and metabolic disease risks mentioned above, obesity-related complications may include fatty liver disease and osteoarthritis. Obesity also increases the risk of many cancers. And finally, it may have profound effects on people's mental health, principally as a result of stigma.
When a patient comes to your office for the first time, what can they expect?
“At the Comprehensive Weight Control Center, our initial visit includes a detailed history of your weight journey and weight-related complications. We discuss your lifestyle, eating pattens and activity level. We offer education on the physiology of weight and the trajectory of weight loss. Working together, we’l help you set goals and agree on a treatment plan that involves a team approach, including dietitians, nurse practitioners, clinical pharmacists and physicians.”
Stay tuned for Part 2 in this series on the obesity epidemic, which will focus on medications for weight loss and type 2 diabetes.
To make an appointment with a provider at the Comprehensive Weight Control Center, call 646-962-2111 or visit the center’s website.