Where do you live? No offense to any of my fellow countrymen but excessive weight gain seems to be the rule in America. I doubt the south american thing plays a part. It's usually more of a lifestyle. Kids or no kids, women tend to get fatter because of poor diet/portion sizes, sitting all day at work, sitting in transit from work to home, sitting in front of TV or on bed or on floor and in front of computer or book etc. I personally think imbalanced diet is the biggest culprit. Too many cheap chemical additives substituting for real ingredients (do you ever read those ingredient labels?!!) Another thing that can affect weight gain is certain medications, especially antidepressants. Don't nag her about this, just try to be kind and join in on the lifestyle changes that she needs to make.