What function does 「しいて」 serve in this sentence?

Question

I have this sentence in a JLPT study textbook, as an example of the use of しいて:

食{た}べたくなければしいて食べることないから、食べられるものだけ食べてね。

The translation is, "If you don't want to eat it, you don't have to, so only eat what you can." I can get that meaning, but, it seems to me that if しいて weren't in the sentence, it would still mean the exact same thing.

食{た}べたくなければ、食べることないから、食べられるものだけ食べてね。

The book says that しいて is "an expression that shows compulsion", and does not give much else for explanation. So it doesn't really say enough to help me see what しいて brings to the party.

What exactly does しいて mean, and how does it make a difference in the two sentences above?

Answer 1

WWWJDIC writes しいて (adv) as 強いて "by force". In your sentence, しいて食べる is roughly equivalent to 無理して食べる, i.e. overdoing it in some way. A more literal translation might be

食べたくなければしいて食べることないから、食べられるものだけ食べてね。
If you don't want to eat anything, don't force yourself (to eat) and just eat as much as you can/want.

Answer 2

In addition to tobiuo's answer, the sentence

食べたくなければ、食べることないから、食べられるものだけ食べてね。

is not equivalent. Here ない means "not necessary" and しいて食べることない means "it is not necessary to force yourself to eat". 食べることない by itself makes little sense in this context.