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In this study, men and women were asked to participate in an 'advertisement study' where they either tried on a bathing suit or a sweater in front of a mirror while also answering a questionnaire; at the end they were invited to eat some cookies. Compared to those that tried on sweaters, women that tried on bathing suits performed significantly worse on the math questions, ate less cookies afterwards as well as filled out more appearance centered "I am" statements.
What is The Swimsuit Study