Despite their normal BMI, metabolically obese individuals – who may comprise as much as 24% of a normal-weight population – may be insulin-resistant and suffer increased cardio-metabolic risks. Likewise, around half of overweight subjects, and 15-45% of obese subjects, appear to have a favorable metabolic profile (that is, no metabolic complications, inflammation, dyslipidaemia, or hypertension).
各体重指数类别观察到的代谢异质性成为支持使用身体成分分析、而非体重指数的进一步证据。比方说，一组体重正常的受试者可能在测出低皮下脂肪量的同时内脏脂肪量却较高。（“外瘦内胖”）。尽管体重指数正常，但代谢肥胖群体——可能在正常体重群体中占比高达24%——可能对胰岛素具有耐药性，同时罹患心脏代谢疾病的风险也增大。同样，大约半数超重受试者和15-45%的肥胖受试者似乎代谢状况良好（也就是不存在代谢性并发症、炎症、血脂异常或高血压）。