The rate of obesity in the United States has reached the epidemic level despite efforts by healthcare providers and patients to improve health-related behaviors and increased efforts to better understand its pathophysiology. “Assessment for excess adiposity is of critical importance,” says Marc-Andre Cornier, MD. To address the issue of assessing adiposity, the American Heart Association (AHA) released a scientific statement to help clinicians. The statement, which was published in the November 1, 2011 issue of Circulation, provides practical guidance for clinical researchers who seek to identify precise measurements for their patients. It also provides recommendations for clinicians who care for patients whose excess weight is a clinical problem.
“Before clinicians can recommend treatment options or talk to patients about obesity prevention, they need to know whether a patient is obese,” says Dr. Cornier, who was the lead author of the AHA scientific statement. He adds that there are also new Medicare guidelines for covering obesity treatment that require clinicians to identify whether or not patients are obese. Medicare will cover provider visits for weight loss counseling in patients who screen “positive” for obesity.
Reviewing the Methodologies for Assessing Adiposity
Healthcare providers and systems are not regularly assessing for excess adiposity with even the simplest, least costly methods, says Dr. Cornier. “Most methods for assessing excess adiposity are not ready for routine clinical use,” he says. “Measuring BMI and waist circumference is currently best to assess adiposity. These are strategies all clinicians should be practicing on a regular basis for patients. Other newer, complex, and more expensive tools are currently available, but physicians need to do a better job utilizing the simpler tools we currently have at our disposal.”
Most of the evidence in the literature on assessing adiposity has been focused on measuring BMI and waist circumference. Waist circumference is a marker of visceral fat, which is associated with fat deposited in the liver, muscle, heart, and other areas thought to be associated with metabolically active fat that causes metabolic disease. “Measuring for body fat composition is of growing importance,” explains Dr. Cornier (Table 1). “More and more studies show that the percent of one’s body that is made up from fat is of far more importance than their weight.”
Fat distribution measurements are also important because they can show clinicians where fat is deposited. This in turn enhances risk assessments (Table 2). While imaging tests like CT and MRI are ideal for assessing fat distribution, both are expensive and therefore not recommended for clinical use in the AHA scientific statement. “Dual-energy X-ray absorptiometry, or DEXA, scanning is commonly used for measuring bone density and could be also used to measure body composition and distribution,” says Dr. Cornier. “Unfortunately, such a strategy is expensive and may not provide more information than a waist circumference or BMI measurement.”
Skinfold thickness is a another simple test that can be used to assess adiposity, but it only looks at one part of the body and focuses only on subcutaneous fat, which has little or no association with metabolic or cardiovascular disease. Hydrostatic weighing is another potential testing option, but Dr. Cornier notes that it is difficult to utilize this tool because it requires patients to be put into a pool. Despite a relatively low associated cost, ultrasound for assessing adiposity has not been studied closely enough, and more research is warranted. “In addition to BMI and waist circumference measurements, utilizing blood tests for various metabolic and cardiovascular disorders is recommended,” Dr. Cornier says. “This combination can provide much information at little cost.”
A Look Into the Future in Assessing Adiposity
Dr. Cornier believes that near infrared interactance and air displacement plethysmography could be clinically relevant methods for assessing adiposity in the near future. “These are strategies that would not be too costly,” he says. “However, bioelectric impedance may be the most practical and inexpensive method. It has the potential to improve the measurement of body composition and may be a cheaper and simpler approach. Although more research is needed, it’s feasible that bioelectric impedence may be ready for greater use in the next 5 to 10 years.”
In the meantime, Dr. Cornier recommends that an emphasis be placed on obesity as a serious societal problem, both medically and financially, that needs to be controlled and prevented. “It’s important that physicians learn how best to assess for excess adiposity and know the associated risk factors. For now, most patients should be assessed for adiposity using BMI and waist circumference measurements.”