The present invention provides fusion peptides having GLP-1 activity and enhanced stability in vivo, in particular resistancy to dipeptidyl peptidase IV. The fusion peptide comprises as component (I) N-terminally a GLP-1(7-35, 7-36 or 7-37) sequence and as component (II) C-terminally a peptide sequence of at least 9 amino acids or a functional fragment, variant or derivative thereof. Component (II) is preferably a full or partial version of IP2 (intervening peptide 2). A preferred embodiment comprises the sequence GLP-1(7-35, 36 or 37)/IP2/GLP-1(7-35, 36 or 37) or GLP-2. The fusion peptide may be produced in engineered cells or synthetically and may be used for preparing a medicament for treating various diseases or disorders, e.g. diabetes type 1 or 2, apoptosis related diseases or neurodegenerative disorders.