According to your description, do you want to know whether a person's mother is fat, his father is thin and his daughter is fat when she grows up? I think this situation exists in real life, but considering that obesity and thinness are 50% probability events, we can't simply draw a conclusion. In fact, from a medical point of view, there is no such provision. Obesity is indeed genetic, but it cannot be simply attributed to the obesity of one's same-sex parents.

First of all, the medical term "obesity" refers to the excessive accumulation of fat in our bodies. There are many reasons for obesity, such as heredity, diet, exercise, neuroendocrine regulation, drugs and so on. Among them, genetic factors do play a role in the formation of obesity, but this inheritance does not necessarily come from same-sex parents.

Secondly, even if same-sex parents have congenital obesity genes, we may not be able to avoid inheritance, but if we eat correctly and exercise properly, that is, keep our mouths shut and separate our legs, then we can correctly reduce the risk of obesity and avoid the consequences of obesity and diseases.

So, you ask this question for your friend, I can understand his worry, but such worry is unnecessary and does not solve the practical problem. To find out the reason, solving the problem is the ultimate goal. Good luck, please accept it if you are satisfied.