Hello!
I'd appreciate a reply and explanation regarding my following question.

Is it possible to use the verb "SUSTAIN" in such a combination:
"to sustain a good body shape''?

Question

Hello!
I'd appreciate a reply and explanation regarding my following question.

Is it possible to use the verb  "SUSTAIN" in such a combination: 
"to sustain a good body shape''?

Answer

You can say it but it sounds formal or technical. In everyday English, we more often say either "stay in shape" or "keep in good shape".

Answer

Yes, that phrase is perfectly fine.

'Sustain' here means keep/maintain.