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One reason may be that public health campaigns branding obesity as a disease are sometimes perceived as being critical of individuals rather than the environmental and social factors that lead to weight gain．
【句型结构】句子主干是One reason may be that…。这是一个that引导的表语从句，且表语从句的主干是public health campaigns．．．are sometimes perceived as．．．，其中branding obesity as…是现在分词作后置定语修饰campaigns，且that lead to weight gain是一个that引导的定语从句修饰factors。
【词汇理解】brand sth．as，意思是“为……打上烙印；给……加上污名”，在句中branding obesity as a disease是现在分词短语充当后置定语。sth．be perceived as sth．，翻译为“将……理解为；将……看作”。be critical of individuals，这个短语的意思是“对个人的批评”。
【译文】原因之一也许是公众健康运动为肥胖打上了疾病的印记。公共健康运动被人们理解为是对肥胖者个人的批评，却忽视了环境和社会因素也可能导致肥胖。