The present invention relates to a novel peptide analog of acylated oxyntomodulin and a pharmaceutical composition for preventing and treating obesity or overweightness, or diabetes accompanied by obesity and overweightness, containing the same, wherein the peptides have dual activation efficacy on receptors of GLP-1/glucagon and increased in vivo half-life, which are superior to those of natural oxyntomodulin, and the pharmaceutical composition containing the same is effective in the treatment of metabolic diseases such as obesity and diabetes.
