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  BMI Obesity has been defined as excessive body fat content. Body mass index (BMI) is a preferred way of determining overweight and obesity because of its simplicity and availability in the clinical environment. BMI is also strongly correlated with mortality and obesity-related comorbid conditions.2,39 The BMI is achieved by dividing the body weight in kilograms by the square of the height in meters. View the BMI chart. Based on NIH guidelines, a patient with a BMI between 25.0 and 29.9 is overweight, and a patient with a BMI of 30 or more is obese. Of significance is that 65% of patients with a BMI of 27 or more have at least one comorbidity — and the chances of multiple comorbidities increase with BMI. 16 Increased BMI is correlated with major health risks (comorbidities), including 7,16,41: Type 2 diabetes Insulin resistance Dyslipidemia Hypertension Cardiovascular disease Gout Osteoarthritis Gallbladder disease Sleep apnea Hypoventilation syndrome Distribution of Body Fat Body fat distribution appears to play a significant mediating role in the health hazards stemming from obesity.21 The typical "android," or male, tendency is to accumulate fat predominantly above the waist — the "apple-shape" distribution. The "gynecoid," or female, pattern is for fat to accumulate predominantly below the waist in the gluteofemoral region (lower abdomen, buttocks, hips and thighs) — the "pear-shape" distribution. Visceral Fat and Risk Factors for Cardiovascular Disease "Upper-body fat has a significantly worse prognosis for morbidity and mortality than does lower-body fat." 46 There is evidence that the intra-abdominal or "visceral" component of upper-body fat (deposited in the omentum and mesentery of the trunk), rather than the subcutaneous component, is primarily responsible for the excess risk. 13,23,46 "Abdominal or android fatness carries a greater risk for hypertension, cardiovascular disease, hyperinsulinemia, diabetes mellitus, gallbladder disease, stroke, and cancer of the breast and endometrium. It also carries a greater risk of overall mortality." 46 * Visceral fat is associated with insulin resistance, which affects lipid and lipoprotein metabolism.21 * In people with high visceral fat, significantly higher triglycerides and significantly lower HDL cholesterol levels were found. 20,21 Waist-to-Hip Ratio A simple, commonly used measure to evaluate regional fat distribution is the waist-to-hip ratio (WHR). It is obtained by measuring the circumferences of the waist at its narrowest point and the hips at their widest (around the buttocks) and simply dividing the values: waist/hips. A WHR of 0.8 to 0.85 in women or of 0.95 to 1.0 in men has been observed to increase health risk.13,30,46 Waist Circumference Some authorities, however, believe that waist circumference and sagittal diameter are more accurate indicators of body fat distribution and health risk than the WHR. 54 For example, waist circumference has been found to be a more accurate predictor of type 2 diabetes than is WHR.12 Bray, writing in Harrison's Principles of Internal Medicine, 14th edition (1998), notes, "A waist circumference above 100 cm [39.4 in] in men and above 90 cm [35.4 in] in women is associated with increased levels of triglycerides and reduced levels of HDL cholesterol."8 However, waist circumference begins to lose predictive power in patients with a BMI of 35 or more; therefore, BMI should be considered in assessing overall risk. 41 To accurately measure waist circumference, first find the iliac crest. Following a horizontal plane around the abdomen, measure the area at the level of the crest. Be sure the tape is not too slack or too taut and is parallel to the ground. Age Whereas many studies suggest that an increase from one's weight at 25 years old may increase mortality, a number have suggested that for the lowest mortality, the pattern of body weight should be leanness in the twenties followed by a very moderate weight gain as one gets older."46 For example, when regression lines showing BMI values with least mortality in men and women from ages 20 to 70 were derived and plotted from a huge database of insurance statistics published as the Build Study, 1979,58 BMI values associated with the lowest mortality climbed steadily with age, 65 as shown in the figure below.2 The Effect of Age on Body Mass Index Associated with Lowest Mortality 
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