If someone or something is an advertisement for something, they show its good effects.

中文解释

现身说法宣传…的好处；是…的活广告 I\'m afraid I\'m not a very good advertisement for the diet since I\'ve actually put on weight! 恐怕我不是这套减肥饮食计划的活广告，因为我的体重实际上是增加了！