This is from the Standard Course Book of HSK5, section 16.
What is the meaning of 多所？
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Not 多所 as one word.
所 is the 量词 for 医学院校
项 is the 量词 for 研究
This 项 study, carried out in conjunction with various 所 medical schools found that,
apart from a few individuals,
the majority people increase their body weight starting on Saturday,
Get fat on Sat!
You could shorten that long and winding first part: