A new consensus statement encourages healthcare professionals to measure the diameter of waists in addition to the index of body mass in order to manage the health and longevity of patients and reduce health risks associated with obesity.
The argument appears in endocrinology journal Nature Reviews. The paper is first published by Robert Ross, who is a professor at the School of Kinesiology and Health Studies at Queen’s University in Ontario, Canada.
Prof. Ross and colleagues review the existing evidence in their argument that the body mass index (BMI) is not sufficient to assess the cardiometabolic health risks of obesity by itself.
Their round-up of “decades of unambiguous facts,” the authors hope, “will encourage health care practitioners and professional societies to regularly include waist circumference in the assessment and treatment of overweight or obese patients.”
Why waist circumference is a ‘vital sign’
Research cited in their statement by Prof. Ross and colleagues found that waist circumference was the strongest predictor of visceral fat (the fat contained inside the abdominal cavity and around many vital organs), which presents the greatest health danger.
Second, they argue for the inclusion of waist circumference guidelines in global obesity surveillance systems, given that abdominal obesity is becoming increasingly common. Not providing guidance on waist circumference alongside BMI may provide an inaccurate picture of the global prevalence of obesity and recent trends, they add.
The researchers also demonstrate that, unlike BMI, waist circumference is a strong predictor of the risk of death. This can be due in part to the waist circumference helping to classify people with large quantities of visceral fat. To conclude, let Prof. Ross and his colleagues write:
“We recommend that measurements of waist circumference and BMI should become a standard part of clinical encounters (that is, an accepted ‘vital sign’).”
Lifestyle changes can affect waist size
In addition, “lifestyle-induced decreases in waist circumference are correlated with increases in cardiometabolic risk factors with or without subsequent weight loss,” writes the writers, adding that waist circumference can be reduced with exercise or diet, “with or without corresponding weight loss.”
The statement clearly continues, “We suggest that waist circumference measurements be collected at the level of the iliac crest or at the midpoint between the last rib and the iliac crest.”
Ultimately, the researchers challenge the current guidelines, “suggest that a single waist circumference standard for white adults (men greater than 102 centimeters[ cm]; women greater than 88 cm) be used to indicate a high waist circumference, regardless of the BMI group.”
Alternatively, Prof. Ross and colleagues recommend a lower threshold for:
- 80 cm for women and 90 cm for men of moderate weight
- 90 cm for women and 100 cm for men with overweight
- 105 cm for women and 110 cm for men with obesity I
- 115 cm for women and 125 cm for men with obesity II and III
“People with scores greater than these levels are at high risk of future coronary problems,” the authors write, and these thresholds suggest a higher health risk within each group of BMI.
Nevertheless, the researchers admit that there are still gaps in knowledge and “refinement of waist circumference threshold values for a given category of BMI across different ages, by sex, and by ethnicity will require further investigation.”
“To address this need, we recommend[…] prospective studies[…] in the populations concerned,” they say. Colleagues and Professor Ross conclude:
The main recommendation of this consensus statement is that waist circumference should be routinely measured in clinical practice, as it can provide additional information for guiding patient management.”