You'd be destroyed by these activists if you said this to their faces. Especially the second part makes no sense.
Have you forgotten that women bear children? If you had to carry additional weight in front of you for 9 months and couldn't work out because it's bad for the baby, you'd get fat too.
Are women always give birth in their whole life?

It takes 9 months to give a birth and 3 months for recovery, after that, they can diet and go to gym, it takes maybe 6-12 months to make them back like when they were single.
You would argue "she had no time because she need to raise the child bla bla", that's why babysitter and housemaid exist, it's pricey? that's why before marriage/have a child, both need to discuss how to have enough money to afford it. Not everyone are lucky? yes, that's why marriage isn't for everyone.
Also, some people get fat because of certain condition like diabetes, so don't put all of them in one basket.
Diabetes patient can go to gym, no excuse.