Pathophysiology of Obesity

Excerpt

Obesity is one of the most common preventable diseases. It is a major public health concern. Obesity has a multifactorial etiology that includes genetic, environmental, socioeconomic, and behavioral or psychological influences. Obesity results from a chronic positive energy balance regulated by a complex interaction between endocrine tissues and the central nervous system.

Obesity measurement can also be used to estimate morbidity and mortality. Body mass index (BMI) has been used to screen overweight and obese individuals. However, waist circumference is the best anthropometric indicator of visceral fat and a better predictor of metabolic disorders such as diabetes, hypertension, and dyslipidemia. People with a normal BMI with a large waist are at higher risk. However, combining BMI and waist circumference adds relatively less risk prediction since they are collinear in nature. Furthermore, hip circumference is inversely related to metabolic syndrome. Large hip circumference is related to lower risks of diabetes and coronary heart disease. This is probably due to having a large muscle mass in the hip region.

Compared to the Body Mass Index (BMI), the Visceral Adiposity Index (VAI) is a more specific and sensitive examination tool. The VAI is, therefore, a reliable indicator of increased patient risk for cardiometabolic diseases. There is currently a lack of scientific knowledge regarding the biochemical and physiologic mechanisms associated with this. A possible explanation for the increased specificity and sensitivity of the VAI is that visceral fat has direct access to the portal venous system, whereas subcutaneous white adipose tissue does not.

Obesity has inflammatory components, directly and indirectly, related to major chronic diseases such as diabetes, atherosclerosis, hypertension, and several types of cancer. Overweight and obese individuals have altered circulatory levels of inflammatory cytokines, such as IL-6, TNFα, C-reactive protein (CRP), IL-18, resistin, and visfatin. Measures of body fat have a stronger correlation with inflammatory markers than BMI.. Exercise and dietary restrictions have been strongly advocated to reduce weight gain and its related complications. Caloric restriction has been proven effective in reducing inflammation in obesity. However, a few studies showed that dietary weight loss has less impact on a long-term anti-inflammatory intervention. On the other hand, regular exercise significantly affects chronic inflammation related to obesity and obesity-associated conditions such as hypertension, diabetes, dyslipidemia, etc.

It is well-documented that obesity and its inflammatory markers have significant effects on hypertension, diabetes, and other chronic conditions. This review provides detailed insight into chronic inflammation, immune and hormonal disturbance related to the pathophysiology of obesity and their effects on chronic conditions.