The following are key points to remember from this American Heart Association (AHA) scientific statement on obesity and cardiovascular disease (CVD):

1. Obesity is a multifactorial disease with a complex pathogenesis related to biological, psychosocial, socioeconomic, and environmental factors, with heterogeneity in the pathways and mechanisms by which obesity is associated with adverse outcomes.
2. The World Health Organization defines overweight as a body mass index (BMI) between 25 and 29 kg/m², and obese as a BMI ≥30 kg/m². Variation by sex, age, and race/ethnicity limits the relationship between BMI and percent body fat. An estimated 603.7 million adults, worldwide, meet criteria for obesity. The prevalence of obesity has doubled between 1980 and 2015 in 73 countries. As of 2015, an estimated 4.0 million deaths are related to obesity.
3. Despite the strong correlation between BMI and abdominal obesity, additional metrics such as waist circumference (WC), an indicator of abdominal obesity, are associated with cardiometabolic disease. WC is predictive of mortality. In fact, some societies recommend measurement of WC in addition to BMI in clinical visits. Visceral adipose tissue (VAT) in the abdominal cavity is positively associated with CV risk. The ratio of WC to height has been used as a predictor of CVD. Waist-to-hip ratio (WHR) has also been shown to predict CV mortality.
4. Pericardial fat, or fat in the pericardial sac, is associated with higher BMI and traditional CV risk factors. However, pericardiac fat is not significantly associated with CV events after adjustment of traditional risk factors.
5. Exercise may reduce VAT, with the most data to support aerobic exercise. However, not all studies have demonstrated this association between exercise and VAT reduction. Data on reductions in epicardial fat with exercise remain inconclusive.
6. The impact of obesity on CV health starts in childhood. Obesity accelerates early atherosclerotic changes including the development of fatty streaks. Obesity is associated with elevated blood pressure, dyslipidemia, and hyperglycemia in children and young adults.
7. Visceral adiposity promotes systemic and vascular inflammation, fundamental to the development of atherosclerosis. In a meta-analysis of over 300,000 adults, at each level of BMI, higher measures of central adiposity (WC and WHR) were associated with an increased risk for coronary artery disease and CV mortality, including those with a normal BMI. Microvascular disease is independently associated with higher BMI, while weight loss (via bariatric surgery) has been associated with improvements in coronary microvascular function.
8. Cardiac testing in the setting of obesity can be challenging. Left ventricular hypertrophy may be underdiagnosed by electrocardiography in the setting of obesity. Imaging testing including computed tomography and stress echocardiography may have higher degrees of artifact and require different protocols for obese versus nonobese patients. Stress cardiac magnetic resonance imaging and positron emission tomography may be the diagnostic tests least affected by obesity.
9. For many CV events, a u-shaped association between BMI and adverse events has been observed. In a large cohort of patients undergoing percutaneous coronary intervention or coronary artery bypass grafting, a u-shaped association for BMI and all-cause mortality, and major adverse cardiac events were observed. BMI may be more strongly associated with heart failure (HF) with preserved ejection fraction compared to HF with reduced EF. A u-shaped curve also appears in the association of BMI with HF outcomes.
10. Obesity may account for 20% of atrial fibrillation (AF) cases. Postoperative AF is also correlated with BMI. Epicardial adipose has emerged as an important proarrhythmic substrate. Weight loss is associated with reduced time in AF and improved success of AF ablations.

Clinical Topics: Arrhythmias and Clinical EP, Cardiac Surgery, Diabetes and Cardiometabolic Disease, Dyslipidemia, Heart Failure and Cardiomyopathies, Invasive Cardiovascular Angiography and Intervention, Noninvasive Imaging, Prevention, Atherosclerotic Disease (CAD/PAD), Atrial Fibrillation/Supraventricular Arrhythmias, Aortic Surgery, Cardiac Surgery and Arrhythmias, Cardiac Surgery and Heart Failure, Acute Heart Failure, Interventions and Coronary Artery Disease, Interventions and Imaging, Computed Tomography, Echocardiography/Ultrasound, Magnetic Resonance Imaging, Nuclear Imaging, Exercise

Keywords: Adiposity, Atherosclerosis, Atrial Fibrillation, Bariatric Surgery, Blood Pressure, Body Mass Index, Coronary Artery Bypass, Coronary Artery Disease, Diagnostic Imaging, Diagnostic Tests, Routine, Dyslipidemias, Echocardiography, Stress, Electrocardiography, Exercise, Heart Failure, Hyperglycemia, Hypertrophy, Left Ventricular, Inflammation, Intra-Abdominal Fat, Magnetic Resonance Imaging, Metabolic Syndrome, Obesity, Obesity, Abdominal, Overweight, Percutaneous Coronary Intervention, Positron-Emission Tomography, Primary Prevention, Risk Factors, Waist Circumference, Waist-Hip Ratio, Weight Loss

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