Show notes
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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Show notes
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 conditions. The independent association of obesity with heart failure pertains almost exclusively to heart failure with preserved ejection fraction (HFpEF) and not heart failure with reduced ejection fraction (HFrEF). The mechanism for this independent association is not well understood and is an area of active research. In mice that are predisposed to obesity have several inflammatory processes that occur locally in the myocardium and systemically that likely contribute to cardiac risk. At the local level, lipotoxicity occurs within the myocardium as it does in nonalcoholic fatty liver disease. At the systemic level, adipose tissue releases adipokines and cytokines that are linked to myocardial damage, injury, and fibrosis. There is a spectrum of metabolic risk among individuals with excess weight. And when obesity is associated with metabolic syndrome in individuals, the risk for cardiovascular disease markedly rises.
4. What are some core tenants of addressing obesity when working with patients when it comes to exercise and diet?
A core tenant of discussing obesity with patients is to discuss it! Obesity is generally under-addressed and under-discussed. Motivation by being positive about risk reduction with a healthier lifestyle can be very effective. Help patients “take time to invest in themselves”. Having them put items on the calendar that include exercise activities, such as taking a walk or going to the gym, can be a useful strategy for patients who are particularly busy with work or school. Stress reduction is an important component to diet and exercise. Smaller activities, a brisk walk or taking the stairs at work can help reduce the activation energy required for exercise and can make exercise feel more attainable to patients. Meal planning and meal timing are both very important aspects to counseling for patients when it comes to healthy eating.
5. What are some tips and tricks on broaching the subject of obesity with patients given the sensitivity of the subject.
It is important to check biases in this space. Obesity should not be considered an individual failing when there is a systemic and societal based issue. We need to think of obesity as a multi-factorial disease that has a behavioral component but also has a more complex societal and biological contribution as well. Approaching the patient with a plan for partnership of management of obesity as a disease, like other diseases such as hypertension and diabetes can be very helpful. Patients want to lose weight, it just becomes very challenging for a variety matters. The weight of the clinician can have an impact as to the discussion of weight in the clinic. For example, clinicians with a higher weight than the patient tend to avoid discussing obesity during clinic visits. Clinicians who have healthy weight statuses can used stigmatizing language when counseling patients. Appreciate that weight management can be challenging and there'll be stops and starts but there can be great outcomes with long-term partnerships with patients.
6. What are the current pharmacologic options for weight loss and when should these agents be considered?
Pharmacological agents should be considered once physical activity and social stressors are addressed. Pharmacological therapy can be a nice adjunct to lifestyle modification, particularly when BMI remains above 30 or when BMI remains 27 with comorbidities. There are a variety of agents such as Orlistat, Liraglutide, Phentermine, Topiramate, and Bupropion. These medications are generally underutilized due to cost and side effects. Some agents have cannot be used long term which may limit their use. The only agent that has been related to cardiovascular risk reduction is Liraglutide.
7. What do we know about the role of bariatric surgery in cardiovascular disease prevention and does weight loss through bariatric surgery provide differential benefit over other forms of weight loss?
Bariatric surgery is probably the most powerful weapon in our obesity arsenal. There are two major subtypes of bariatric surgery. There is a restrictive subtype, such as a sleeve gastrectomy, and a malabsoptive subtype, such as a gastric bypass surgery. The Roux-en-Y gastric bypass has both the malabsorptive and restrictive components. There is prospective data that shows that bariatric surgery is associated with more weight loss than lifestyle modifications. Bariatric surgery is also shown to be associated with a reduction in comorbidities like hypertension, diabetes and dyslipidemia. Bariatric surgery is also associated with a reduction in pathophysiological processes like inflammation and endothelial dysfunction. Prospective studies with matched data, such as the Swedish Obesity study cohort, bariatric surgery has been associated with a reduced risk in cardiovascular disease events and a markedly improved survival. There have been significant risk reductions in heart failure as well. Most cardiovascular disease reductions seen with bariatric surgery occur through the profound weight loss that occurs after surgery. Risk calculators such as https://riskcalc.org/BariatricSurgeryComplications/ can help guide clinicians and patients when considering bariatric surgery.
BMIWHO ClassificationBelow 18.5Underweight18.5-24.9 Normal weight25.0-29.9Pre-obesity 30.0-34.9Obesity class I35.0-39.9Obesity class 2 40.0Obesity class 3
Cardionerds Cardiovascular Prevention Series
The Cardionerds CV prevention series includes in-depth deep dives on so many prevention topics including the ABCs of prevention, approach to obesity, hypertension, diabetes mellitus and anti-diabetes agents, personalized risk and genetic risk assessments, hyperlipidemia, women’s cardiovascular prevention, coronary calcium scoring and so much more!
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