No, it is not. It does not work as an analogy.

An anorexic person does not NEED dieting. On the most general level, an anorexic person needs to get in touch with reality - to realize that he or she does not need dieting, he or she needs to get in touch with reality.

Contrast to, say, skin improvement suggestions.

You should be able to realize that, say, topical tretinoids REALLY improve skin... really - in reality, whereas dieting does not work, in reality.

So, there is no relationship between suggesting topical retinoids to a BDD person, since any person, BDD or not, can benefit from them IN REALITY (barring extra sensitive skin which is rare), but nobody (<5% of those who engage in dieting) can benefit from tips about dieting IN REALITY.

If an anorexic person listens to tips on dieting, he or she will only get more anorexic, right?

If a BDD person listens to tips on skin care and protection, he or she will get better skin and will not get MORE BDD - either will stay the same, or, improve. The general notion is "do no harm". Not "do good", but "do no harm". Right?

So tips on dieting given to anorexics do harm.

And retinoid tips given to anybody do no harm.

A very big difference. Night and day.