Obesity as a Disease

doi:10.1016/j.mcna.2017.08.004

Medical Clinics of North America

Volume 102, Issue 1, January 2018, Pages 13-33

https://doi.org/10.1016/j.mcna.2017.08.004 Get rights and content

Section snippets

Key points

•
Obesity is a complex disease with many causal factors.
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Obesity is associated with multiple comorbidities contributing to significant morbidity and mortality.
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Various peripheral and central mechanisms play a role in the development of obesity.

Causes or mechanisms of obesity

Obesity is a disease that has rapidly escalated over the past several decades and is caused by environmental, humoral, and genetic factors, likely working in combination. The environmental factors contributing to the increase in obesity include but are not limited to decreased physical activity; increased television watching times and sedentary lifestyle⁸; increased food consumption, particularly of energy-dense, high-calorie, palatable food served in increasing portion sizes9, 10; and the use

Metabolically healthy versus unhealthy

BMI is most frequently used for the classification of obesity. Mortality, morbidity, and complications increase with the grade of obesity. Grade II and III obesity (BMI equal to or greater than 35 kg/m² and equal to or greater than 40 kg/m², respectively) have been associated with increased risk of cardiovascular disease and comorbidities compared with grade I obesity (BMI 30–35 kg/m²).103, 104, 105, 106 However, there is a known subset of the obese population devoid, in the short-term, of

Metabolic syndrome, diabetes, and cardiovascular disease in relation to obesity

Obesity is associated with increased mortality.⁶ Each 5 kg/m² increase in BMI above 25 kg/m² increases overall mortality by approximately 30%; vascular mortality by 40%; and diabetic, renal, and hepatic mortality by 60% to 120%.⁶ At 30 to 35 kg/m², median survival is reduced by 2 to 4 years and at 40 to 45 kg/m² by 8 to 10 years.⁶ The main causes of death include ischemic heart disease,¹¹⁴ stroke¹¹⁵ and diabetes-related complications.⁶ The vicious cycle resulting in increased mortality in

Polycystic Ovarian Syndrome

There is a confirmed relationship between obesity and PCOS. The prevalence of obesity in women diagnosed with PCOS is as high as 80% in the United States.¹⁴⁴ PCOS is characterized by increased production of androgens, which affects the hypothalamus-hypophysis-ovarian axis (HHOA) and may affect fertility.¹⁴⁵ Obesity is considered a factor in the pathophysiological cascade of PCOS through 2 major pathways: IR and hyperandrogenism.¹⁴⁵ However, obesity can also be considered a complication of PCOS,

Summary

Obesity has emerged as an epidemic that poses an unprecedented public health challenge. Historically known to be a rare disease of the affluent, this disease has now flipped the coin and is more prevalent among the lower socioeconomic and less-educated classes. Although multiple risk factors have been identified for obesity, a deeper understanding of how these factors interact is yet to be determined. Major determinants and contributors of the obesity epidemic are the highly processed,

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