20656
Patients lost 7 . 3 kg ( 8 . 1 - 6 . 5 ) during the presurgery period versus 4 . 0 kg ( 6 . 2 - 1 . 7 ) during the postsurgery period ( P = 0 . 01 between periods ) .
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Please list all entity words in the text that fit the category.Output format is "type1: word1; type2: word2". 
Option: Chemical 
Text: {0} 
Answer:
 None