Most COCs do not necessarily cause weight gain in a significant amount. The average increase in weight specific to COCs is 2 kilos on average. Since each woman metabolizes drugs according to her own specific chemistry this can fluctuate. If weight gain is seen as a significant issue and changes in diet and exercise have been ruled out, a change to a different type of Progesterone can be considered. Estrogen is estrogen but progesterone is typically the culprit when issues where COCs are concerned.