The present invention relates to a pharmaceutical composition containing ATPase inhibitor factor 1 (ATPIF1) as an active ingredient for the prevention or treatment of diabetes or diabetic complications, and to a pharmaceutical composition containing ATP1F1 as an active ingredient for prevention or treatment of obesity. The composition containing ATPIF1, according to the present invention, has a diabetes treatment effect by promoting sugar absorption in muscle cells and improving insulin sensitivity, and has an obesity prevention or treatment effect by effects of suppressing fat synthesis in fat cells and promoting the browning of fat cells.
