It sounded to me that the major risks were the increased likelihood of becoming diabetic. And that's upsetting. It sounds like they took the next 3 generations, fed them healthily and they still had greater risk of becoming diabetic compared to healthy mice born of healthy mothers.  Obesity doesn't have to happen ever. But if a fat doesn't care for herself before getting pregnant, she can cause tangable harm to the next couple generations even if they care well for themselves.