A method is provided, comprising feeding a cat a foodstuff comprising a protein to fat ratio of 1:0.27 to 1:0.63 on a gram:gram as fed or dry matter basis, and measuring the level of glucose-dependent insulinotropic polypeptide (GIP) in a blood sample from the cat before and after feeding the foodstuff. A reduction in GIP levels and/or maintaining low levels of GIP post-prandially is indicative of a foodstuff useful in preventing accumulation of and/or reducing body fat in a cat and therefore controlling the body weight of a cat.
