The present invention is related to a nucleic acid, preferably binding to ghrelin, whereby the nucleic acid comprises a first stretch Box A, and a second stretch Box B, whereby the first stretch Box A comprises about 25 consecutive nucleotides, the second stretch Box B comprises about six to eight consecutive nucleotides, whereby a 3&prime；-terminal stretch of nucleotides of the first stretch Box A hybridizes with the second stretch Box B, whereby upon hybridization a first double-stranded structure is formed, whereby such first double-stranded structure comprises a bulge.
