The invention concerns a peptide based on biologically active CCK-8. The peptide has improved characteristics for the treatment of at least one of obesity and type 2 diabetes and has the structure: (Z)-Asp.sup.1-Aaa.sup.2(X)-Aaa.sup.3Gly.sup.4Trp.sup.5Aaa.sup.6Asp.sup.7(Y- )Aaa.sup.8K, wherein the amino acids may be either D or L amino acids; the bond between amino acid residues is either a peptide bond or a non-peptide isostere bond; Aaa.sup.2 is selected from the group comprising Tyr and Phe; when Aaa.sup.2 is Tyr, X is selected from the group comprising SO.sub.3H.sup.-, PO.sub.3H.sub.2.sup.- and a polymer moiety of the general formula --O--(CH.sub.2--O--CH.sub.2).sub.n--H, in which n is an integer between 1 and about 22, wherein the X is covalently bound to the para phenyl oxygen of Tyr, and, when Aaa.sup.2 is Phe, X is CH.sub.2SO.sub.3Na, wherein the X is covalently bound to the para phenyl position of Phe; Aaa.sup.3 is selected from the group comprising Met, norleucine, 2-aminohexanoic acid and Thr; Aaa.sup.6 is selected from the group comprising Met, norleucine, 2-aminohexanoic acid and Phe; Aaa.sup.8 is selected from the group comprising Phe and Met; Y is covalently bound to the nitrogen of Aaa.sup.8 and is selected from the group consisting of H and CH.sub.3; K is selected from the group consisting of the hydroxyl group of Phe.sup.8, an amide covalently bound to Phe.sup.8, an ester covalently bound to Phe.sup.8, a salt of the hydroxyl group of Phe.sup.8, a salt of an amide covalently bound to Phe.sup.8, a salt of an ester covalently bound to Phe.sup.8 and a polymer moiety of the general formula --O--(CH.sub.2--O--CH.sub.2).sub.n--H, in which n is an integer between 1 and about 22; and Z comprises at least one amino acid modification, wherein said at least one modification comprises an N-terminal extension, or an N-terminal modification, but excludes Asp.sup.1-glucitol CCK-8 where Aaa.sup.2 is Tyr and X is SO.sub.3H.sup.-. The peptides, and Asp.sup.1-glucitol CCK-8, are useful to at least one of inhibit food intake, induce satiety, stimulate insulin secretion, moderate blood glucose excursions, enhance glucose disposal and exhibit enhanced stability in plasma compared to native CCK-8