Not attracted to wife body anymore

I know this will come out as being harsh but I'm not attracted to my wife physically anymore.

We've been married for 13 years and have 2 kids together. She is a great wife and mom and does a lot for all of us. I really love her and not looking to leave. But I'm jus not attracted to her as much as I use to be

She's gained significant amount of weight since the kids, she exercises but can't see to lose the weight. Could be something genetic. I'm supportive about her changing up her diet and getting a trainer but nothing seems to work

I feel like an ass for thinking this way, but I'm not even excited to have sex anymore. We prob do it once a month if that. We usually finish fast due to lack of action. I know people change over time and I don't expect her to be the same body as when we got married. I feel anxious and sad for thinking this but I know I'm not happy in the current situation.

Any advise out there