CardioNerds (Carine Hamo, Amit Goyal, and Daniel Ambinder) discuss the obesity epidemic and how it relates to the cardiovascular system with Dr. Chiadi Ndumele, cardiologist and epidemiologist at The Johns Hopkins Hospital and chairs the obesity subcommittee of the American Heart Association (AHA). They cover obesity definitions, epidemiology, strengths and limitations of different biometrics, including BMI, impact on myocardial structure and function, and current pharmacologic & surgical options for weight loss. They also discuss the practical approach to addressing obesity with patients. This episode was produced by Dr. Carine Hamo. Show notes & references by Dr. Daniel Ambinder.
Episode graphic by Dr. Carine Hamo
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1. What is obesity and how do we define it at the personal and population level?
Obesity is when there is an excess and often dysfunctional adipose tissue that contributes to morbidity and to premature mortality The metric used to define obesity is Body Mass Index (BMI), defined as a person's weight in kilograms divided by the square of the person's height in meters (kg/m2) See WHO BMI classification below
2. What is the current epidemiology of obesity and are there certain populations that are affected more than others?
Rates of obesity are climbing. Currently, around 70% of the population meets criteria for being either overweight or obese and ~40% are at the level of obesity. Minorities such as African Americans, Native Americans, and Latinos have higher rates of obesity. Higher rates of obesity are also seen in groups with lower socioeconomic status. Certain populations, such as Southeast Asians, tend to develop severe metabolic consequences of obesity such as insulin resistance and cardiovascular consequences with less excess weight than other populations. Adult weight is very important but weight history (long standing obesity) plays a role as well when it comes to cardiovascular risk associated with obesity.
3. Currently the WHO classifies obesity based on BMI. What are the limitations to using BMI as a measure of obesity? Are their benefits to measuring waist circumference instead?
BMI is a far from a perfect measure but it correlates nicely at the population level with cardiovascular events and premature mortality BMI is more accessible than a direct quantitative or functional measure of adipose tissue A major limitation of BMI is that it does not reflect body composition. Body composition is very important in understanding risk associated with obesity. For example, football players may fall into the category of grade 1 obesity if just using BMI to classify their weight status. Waist circumference (WC) is a good way of getting a sense of body composition. Abdominal obesity is most closely linked to insulin resistance and various metabolic consequences such as diabetes, hypertension, and inflammation. This is why WC is incorporated into the metabolic syndrome construct. Adding WC measurements to the BMI measurements, particularly for individuals in the overweight and grade 1 obesity group (BMI 25-29.9, and 30-34.9) provides significant prognostic information about the development of cardiovascular disease.
4. How do obesity and metabolic syndrome impact myocardial structure and function? How does obesity and increased adiposity fit into the larger scheme of metabolic risk and metabolic syndrome?
Obesity is independently associated with myocardial remodeling and with increased heart failure risk. This contrasts with coronary heart disease (CAD) and stroke. For CAD and stroke, most associations with obesity are largely mediated by diabetes, hypertension and dyslipidemia. However, in heart failure, there is a strong unexplained association that remains after you consider those associated ...