No matter what health history, it's more common than not to gain weight more easily as we age. I really wish that weren't the case. For women, hormones have a part in that. Have you talked to your doctor about a healthy diet that would suit your tastes?
It all comes down to calories (eating fewer calories). Fitday has tools for watching that, setting goals, etc. You can also see carbs, protein, fat, etc. Try out the food log if you haven't already!