Re: No Egg Production.
Does your sister have PCOS? That is what it sounds like to me if she has had trouble getting pregnant for so long now. Though weight can often lead to women not ovulating, it is also well documented that PCOS, which is a hormone imbalance that can lead to anovulation, that women can gain weight rapidly and have a hard time taking the weight off. My sister suffers from PCOS and has not been able to get pregnant and just keeps getting bigger and bigger. She went through rounds of hormones for three years while she was married and never was able to start producing eggs.
I would imagine that she has at least been tested for PCOS if she has been seeking professional help, these just definitely sound like the symptoms my sister has experienced. I know that a very fresh diet helps women with PCOS a lot; fresh meats, veggies, and cheeses (only go around the outside circle of a grocery store).
I hope she finds out the issue, if she has not already, and I wish you all the best of luck!