Rationale:

• BMI has a good correlation with risks associated with obesity and body fat, such as diabetes, heart disease, osteoarthritis, gall bladder disease, and certain types of cancer.

Evidence:

• The National Heart, Lung and Blood Institute and World Health Organization define normal weight range as BMI 18.5 to 24.9, overweight as BMI 25 to 29.9, and obesity as BMI >30 kg/m² (151; 152). For Asians, BMI >23 kg/m² is defined as overweight, and BMI >25 kg/m² is defined as obese (287).
• At the same BMI, body fat is about 12% higher in women than men (288).
• Measuring BMI is recommended by the National Task Force on the Prevention and Treatment of Obesity for adults (289) and for children (56).
• The amount of body fat at the same BMI is related to ethnicity (288).
• BMI is related to risk of heart disease (127; 164; 204; 205; 206), diabetes (128; 180), and hypertension (229; 230; 231). The first episode of chronic heart disease is predicted by high BMI as well as by higher systolic BP, higher cholesterol/HDL cholesterol ratio, and diabetes in the Framingham study (290).
• BMI is related to osteoarthritis (244; 245; 246; 247) and gall bladder disease (223; 224; 225).
• BMI is related to increased risk of cancer of the breast, endometrium, prostate, colon, kidney, and gall bladder, as well as greater risk of gastroesophageal reflux disease (227; 283; 291).
• A cost-effectiveness analysis suggests that screening for impaired glucose tolerance may be appropriate given the rise in prevalence of obesity and diabetes (292).

Comments:

• Although BMI is widely used, its accuracy is limited in people with BMI <30. Above 30, BMI has good specificity but misses more than half of the people with excess fat (293).