This invention relates to an oil composition, preferably obtained from a copepod, and the use thereof to reduce accumulation of visceral fat and counteract impairment of heart function caused by obesity inducing Western diets. The oil composition of the present invention can thus be used to reduce abdominal obesity and improve glucose tolerance and thus to reduce the risk of obesity related diseases such as but not limited to type 2 diabetes or cardiovascular disease, or to prevent or treat such diseases.