We mean that all readers lose the ability to define the image of a healthy body as based on critical measures of health.

【直译】我们的意思是，所有读者都失去了将健康身体的概念定义为基于健康关键指标的能力。

【意译】我们的意思是，所有读者都失去了根据健康的关键指标来定义健康身体概念的能力。

我注意到：Expert 的解释是as based on 跟 as shown on 类似。

这是风马牛不相及的两个词组和用法。

前者as 跟define 搭配，引出“宾语补足语”；后者as shown 引出比较结构。绝对不是一个概念！

要想理解这个问题，就要从define 的用法说起：

及物动词define 与as 连用时,表示“把…定义为”。as 后面可以接“名词、形容词、分词短语等”作宾补。本句结构是：define + 宾语 + as + 过去分词（based）。

as 引出宾语补足语，常跟as 连用的动词，归纳如下：

该类动词表示“认为，认可，承认，确认，当作，看作，视为，理解为，定义为”等含义。为了理解方便，我们用him 作宾语。

观点类“regard sb. as... 型结构”归纳如下：

regard him as

define him as

consider him as

identify him as

view him as

recognize him as

confirm him as

think of him as

look on him as

look upon him as

esteem him as

reckon him as

acknowledge him as

know him as

conceive of him as

see him as

treat him as

count him as

value him as

accept him as

take him as

label him as

perceive him as

fancy him as

imagine him as

understand him as