by Bianca Garilli, ND
Body mass index (BMI) is used in the medical community for defining anthropometric height/weight characteristics.1 An individual’s BMI categorizes them as normal, overweight or obese and is often used as a risk factor for various chronic health issues including coronary artery disease (CAD).1 It has become apparent however that BMI is a gross estimate of adiposity; BMI is a poor indicator of percent of body fat and does not indicate site of body fat distribution, an increasingly important parameter for assessing risk of CAD and associated mortality.1,2
A population-based, study at the Mayo Clinic in Rochester, Minnesota utilized medical records to test whether different measures of obesity and location of fat distribution predict future cardiovascular events.3 The study authors hypothesized that central adiposity as measured by waist-to-hip ratio (WHR) would be associated with increased major cardiovascular events (MACE), whereas obesity as assessed by BMI would either have none or paradoxical association (i.e., “obesity paradox”, such that higher BMI confers a survival advantage for heart failure)4 with MACE.3 MACE was a composite outcome in this study defined as:3
- Any diagnosis of a new acute coronary syndrome, including both ST and non-ST segment elevation MI and unstable angina that required hospitalization
- Coronary revascularization, including percutaneous coronary intervention and coronary artery bypass grafting
- Stroke, including any non-traumatic brain hemorrhage or infarction
- Ventricular arrhythmias warranting in-hospital management
- Death from any cause
Study participants were CAD patients who had originally been referred for cardiac rehabilitation following a myocardial infarction, stable or unstable angina, and coronary revascularization by either coronary artery bypass grafting or percutaneous coronary intervention.3
Characteristics of the 1529 participants included:3
- 74% male
- 40% obese by BMI
- 88% of males and 57% of females had central obesity by WHR
- Mean age: 63 years
- Median follow-up: 5.7 years
Results demonstrated that obesity by BMI was not associated with MACE in men nor women.3 Higher WHR however, was a significant predictor for MACE in women (HR: 1.85, CI: 1.16-2.94; p=0.01), but not in men. This finding was independent of BMI (controlled for in statistical models) and consistent with previous studies which had shown associations between higher WHR and increased CV- and mortality risk in women across all BMI categories.3
The risk of MACE for women in the highest WHR tertile was found to be almost 2-fold higher than those in the lowest WHR tertile; this relationship did not change after adjusting for BMI.3 Males in the highest WHR tertile did not experience this same increase in risk.3
The study’s authors discuss several potential reasons for these gender-specific differences including the fact that women’s fat distribution changes post-menopause resulting most typically in an increase in waist circumference (WC) and a decrease in hip circumference (HC), due to a greater fat deposition in pelvic and gluteofemoral muscle regions. Males, on the other hand, store more of their fat viscerally, creating a less dramatic shift in their WHR. The authors recommended follow-up studies to determine if increased WHR in post-menopausal women results in higher androgen production and thus, higher numbers of CVD events. 3
Why is this Clinically Relevant?
- Women with CAD and high WHR have a higher risk of MACE, regardless of BMI3
- Men with CAD and high WHR do not appear to carry this same increase in MACE as their female counterparts of similar age
- Focusing on achieving a healthy WHR in women may be more important than a “normal” BMI goal to reduce risk of MACE
- Nuttall F. Body mass index – obesity, BMI, and health: a critical review. Nutr Today. 2015;50(3):117–128.
- Elffers TW, de Mutsert R, Lamb HJ, et al. Body fat distribution, in particular visceral fat, is associated with cardiometabolic risk factors in obese women. PLoS One. 2017;12(9):e0185403.
- Medina-Inojosa JR, Batsis J, Supervia M, et al. Relation of waist-hip ratio to long-term cardiovascular events in patients with coronary artery disease. Am J Cardiol. 2018;121(8):903-909.
- Nagarajan V, Kohan L, Holland E, Keeley E, Mazimba S. Obesity paradox in heart failure: a heavy matter. ESC Heart Fail. 2016;3(4):227-234.