Obesity, metabolic syndrome, and cardiovascular disease

Obesity is rampant in the United States and is becoming increasing common worldwide. The increase in obesity prevalence is due to two major factors, plentiful supplies of inexpensive foods and sedentary jobs. Both are driven in no small part by technology. Thanks to technology, production of large quantities of cheap food is possible, and manual work is rapidly disappearing. In areas of the world in which these advances have not penetrated, obesity is not a significant public health problem. Thus, obesity is a direct result of technological advance and represents a major challenge for technological society. Obesity must also be recognized as a product of free society in which a multitude of food choices and job opportunities are available. A public health approach to the problem of obesity that restricts choice will not be acceptable to a free society. This fact puts increased responsibility on the individual to recognize the underlying causes of obesity and modify behavior to reduce the personal burden of obesity. That obesity extracts a social cost is well recognized. The costs in physical health are less well recognized by the general public. The foremost physical consequence of obesity is atherosclerotic cardiovascular disease (ASCVD) (1). A substantial portion of the ASCVD resulting from obesity is mediated by type 2 diabetes. But obesity is accompanied by several other risk factors for ASCVD. The sum of the risk factors that predisposes to ASCVD goes by the name of metabolic syndrome. In addition, obesity is accompanied by other medical complications other than ASCVD and diabetes; these include fatty liver, cholesterol gallstones, sleep apnea, osteoarthritis, and polycystic ovary disease. These disorders are commonly found in individuals who carry the metabolic syndrome. Obesity can be called an underlying risk factor for cardiovascular disease (ASCVD) (2). It is called this because it raises the risk for ASCVD through other risk factors. The latter include the major risk factors (hypercholesterolemia, hypertension, hyperglycemia) and emerging risk factors (atherogenic dyslipidemia, insulin resistance, proinflammatory state, prothrombotic state). The relationship of obesity to major and emerging risk factors varies, depending on the genetic and acquired characteristics of individuals. The majority of obese persons who develop ASCVD typically have a clustering of major and emerging risk factors (metabolic syndrome). The constellation of major and emerging risk factors that make up the metabolic syndrome can be called metabolic risk factors (3). This article will first examine the variable characteristics of obesity; this will be followed by an examination of the relation of obesity to the metabolic syndrome; and finally, the relation of the metabolic syndrome to ASCVD will be reviewed. Categories of obesity Obesity can be defined as an excess of body fat. A surrogate marker for body fat content is the body mass index (BMI), which is determined by weight (kilograms) divided by height squared (square meters). In clinical terms, a BMI of 25–29 kg/m 2 is called overweight; higher BMIs (30 kg/m 2 ) are called obesity (4). A better way to define obesity would be in terms of percent total body fat (4). This can be measured by several methods (skin-fold thickness, bioelectrical impedance, underwater weighing). In terms of percent body fat, obesity can be defined as 25% or greater in men and 35% or greater in women. The measurement of percent body fat is rarely used in clinical practice, however, because of inconvenience and cost.