Pharmaceutical composition comprising (a) a (poly)peptide which comprises or consists of the amino acid sequence glutamine-glutamic acid-proline; or a derivative of the amino acid sequence QEP selected from the group consisting of: (a) QSt hiophosphate -P; (b) QSP, wherein the S residue is phosphorylated; (c) QDP; (d) QYP; (e) QTP; (f) QTP, wherein the T residue is phosphorylated; (g) QT thiophosphate -P; (h) NEP; (i) NSP, wherein the S residue is phosphorylated; (j) NS thiophosphate -P; (k) NDP; (l) QE- hydroxy P; (m) QD- hydroxy P; (n) QS- hydroxy P, wherein the S residue is phosphorylated; (o) QS thiophosphate-hydroxy P; (p) any one of (a) to (o) having its first amino acid residue replaced by N; and (q) any one of (a) to (p) having its last amino acid residue replaced by hydroxy P, wherein said derivative is capable of reducing/inhibiting SGLT1-mediated glucose and/or galactose uptake into a cell in the presence of an increased concentration of glucose and/or galactose, (b) a nucleic acid molecule encoding the (poly)peptide of (a); or (c) a vector comprising the nucleic acid molecule of (b) for use in the prevention or in the treatment of a disease or disorder selected from the group consisting of obesity, diabetes mellitus and hyperglycemia, wherein said pharmaceutical composition is to be administered to a patient having an increased concentration of glucose and/or galactose in the lumen and/or in the epithelial cells of at least one part of its gastrointestinal tract. (a) a (poly)peptide which comprises or consists of the amino acid sequence glutamine-glutamic acid-proline; or a derivative of the amino acid sequence QEP selected from the group consisting of: (a) QSt hiophosphate -P; (b) QSP, wherein the S residue is phosphorylated; (c) QDP; (d) QYP; (e) QTP; (f) QTP, wherein the T residue is phosphorylated; (g) QT thiophosphate -P; (h) NEP; (i) NSP, wherein the S residue is phosphorylated; (j) NS thiophosphate -P; (k) NDP; (l) QE- hydroxy P; (m) QD- hydroxy P; (n) QS- hydroxy P, wherein the S residue is phosphorylated; (o) QS thiophosphate-hydroxy P; (p) any one of (a) to (o) having its first amino acid residue replaced by N; and (q) any one of (a) to (p) having its last amino acid residue replaced by hydroxy P, wherein said derivative is capable of reducing/inhibiting SGLT1-mediated glucose and/or galactose uptake into a cell in the presence of an increased concentration of glucose and/or galactose, the amino acid sequence glutamine-glutamic acid-proline; or a derivative of the amino acid sequence QEP selected from the group consisting of: (a) QSt hiophosphate -P; (b) QSP, wherein the S residue is phosphorylated; (c) QDP; (d) QYP; (e) QTP; (f) QTP, wherein the T residue is phosphorylated; (g) QT thiophosphate -P; (h) NEP; (i) NSP, wherein the S residue is phosphorylated; (j) NS thiophosphate -P; (k) NDP; (l) QE- hydroxy P; (m) QD- hydroxy P; (n) QS- hydroxy P, wherein the S residue is phosphorylated; (o) QS thiophosphate-hydroxy P; (p) any one of (a) to (o) having its first amino acid residue replaced by N; and (q) any one of (a) to (p) having its last amino acid residue replaced by hydroxy P, wherein said derivative is capable of reducing/inhibiting SGLT1-mediated glucose and/or galactose uptake into a cell in the presence of an increased concentration of glucose and/or galactose, (a) QSt hiophosphate -P; (b) QSP, wherein the S residue is phosphorylated; (c) QDP; (d) QYP; (e) QTP; (f) QTP, wherein the T residue is phosphorylated; (g) QT thiophosphate -P; (h) NEP; (i) NSP, wherein the S residue is phosphorylated; (j) NS thiophosphate -P; (k) NDP; (l) QE- hydroxy P; (m) QD- hydroxy P; (n) QS- hydroxy P, wherein the S residue is phosphorylated; (o) QS thiophosphate-hydroxy P; (p) any one of (a) to (o) having its first amino acid residue replaced by N; and (q) any one of (a) to (p) having its last amino acid residue replaced by hydroxy P, (b) a nucleic acid molecule encoding the (poly)peptide of (a); or (c) a vector comprising the nucleic acid molecule of (b)