Compounds of formula (I); wherein R.sub.1 and R.sub.2 are the same or different and may be selected from the group consisting of a hydrogen atom, a hydroxy group, an alkyl group, a halogen atom, an alkoxy group, an acyloxy group, an acyl group, an alkenyl group, an alkynyl group, an aryl group, an alkylthio group, an alkoxycarbonyl group, an alkylsulfinyl group, an alkylsulfonyl group, an amino group, and an alkylamino group; and X represents a carboxylic acid group, a carboxylate group, or a carboxamide group; or any pharmaceutically acceptable salt, solvate, complex or pro-drug thereof, with the provisos that the compound of formula (I) is not (all-Z)-4,7,10,13,16,19-docosahexaenoic acid (DHA), alpha-methyl DHA, alpha-methyl DHA methyl ester, alpha-methyl DHA ethyl ester or alpha-hydroxy DHA ethyl ester, are disclosed. A fatty acid composition and a pharmaceutical composition comprising such compounds are also disclosed. The use of such compounds as medicaments, in particular for the treatment of diabetes type 2, is also disclosed.