The body mass index (BMI), or Quetelet index, is a heuristic proxy for human
body fat based on an individual's weight and height. BMI does not actually
measure the percentage of body fat.
The body fat percentage (BF%) of a person or animal is the total weight of
fat divided by total weight.
1）BF%，身体肥胖率是测量健壮的方法（不考虑身高体重）。
2）Body Fat 包括两种：essential body fat （必须的） and storage body fat （
储存的）。
女人的EBF高于男人，因为生孩子和荷尔蒙的分泌。（3%–5% in men， 10-16% in
women）。
SBF存在于肌肉组织中，部分地起到保护器官的作用。
The table below from the American Council on Exercise (not an official
government agency) recommends the following percentages:[3]
Description Women Men
Essential fat 10–13% 2–5%
Athletes 14–20% 6–13%
Fitness 21–24% 14–17%
Average 25–31% 18–24%
Obese 32%+ 25%+
一种由BMI计算BF%的方法：
Child body fat % = (1.51 × BMI) − (0.70 × Age) − (3.6 × sex)
+ 1.4
Adult body fat % = (1.20 × BMI) + (0.23 × Age) − (10.8 × sex) - 5.4
where sex is 1 for males and 0 for females.
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more infor. http://en.wikipedia.org/wiki/Body_fat_percentage
