来自《耶鲁大学开放课程：有关食物的心理学、生物学和政治学 第5集 第5集》

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  estimate from that how much body fat a person actually has.
  从而估算一个人的体内脂肪含量
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  The most precise way, the gold standard of measuring this,
  最精确的方法 金标准
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  is to weigh people under water
  就是检测水下体重
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  which is what you see in the upper left.
  就是你们在左上角看到的
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  A person sits on a chair,
  一个人坐在椅子上
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  is submerged in water for just a very short time,
  很快的潜入水中
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  and their body fat can get estimated from that
  以此来估测体内脂肪含量
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  because lean tissue and fat tissue have different densities
  因为瘦肌肉组织和脂肪组织的密度不同
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  and that can be determined through calculations.
  可以通过计算得出结果
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  Of course you could imagine
  当然 你可以想象
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  how this is difficult to do with large numbers of people
  要对大批量的人群进行测试有多困难
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  and if you have to have the right equipment.
  而且你必须要有相应的装置