Oxyntomodulin analogues offer a novel treatment for obesity. However during analogue screening in a rat model increased food intake was consistently observed. To further investigate this finding, a series of representative analogues (OXM14 and OXM15) and their Glu-3 equivalents (OXM14E3 and OXM15E3) were administered to rats for 7 days and food intake and bodyweight measurements taken. To investigate the role of glucagon receptor activation glutamate (Glu/E) was substituted at amino acid position 3. GLP‑1 and glucagon receptor efficacy of the oxyntomodulin analogues and their Glu‑3 counterparts were measured at the rat receptors in vitro. Doses of 25nmol/kg of OXM14 and OXM15 increased food intake by up to 20%. Bodyweight was not significantly increased. Food intake was not increased with the Glu‑3 peptides, indicating that a glucagon receptor mechanism may be responsible for the increase in food intake.