Fatphobia and fat rights are very much a reproductive rights issue.
For one thing, the entire support structure of the right to choose to end a pregnancy or to not have a child or to only have as many children as you choose to-- this is based on the idea that your body is yours. That no one, and especially not the government, has a right to interfere with someone's body autonomy.
That's why anti-choice arguments never fly. No one has the right to force you to let them use your body. If someone will die because you don't give blood- that's not ideal, but no one supports the government strapping people down and taking their blood through force.
Well, I'm here to tell you that fat bodies have rights too. That the same body autonomy argument holds true for the idea that no one has any business trying to force people below a certain weight.
Fat women get subpar gynecological care that they have to pay more to access. I'd also be willing to bet cash money that the extreme amounts of medical fatphobia is also a barrier for fat trans people who need access to gynecological care.
Fat women are denied access to fertility treatments until they lose weight.
Fat people are less likely to be seen as good candidates for adoption.
Some doctors won't do pap smears on fat women, which could lead to a missed cervical cancer diagnosis.
Fat women have more unplanned pregnancies because the birth control dosages were never tested on fat women, and the dosages are not adjusted for fat people. Plan B does not work reliably on fat bodies.
Doctors miss the pregnancies of fat women b/c they refuse to believe we are sexually active so we can miss deadlines for abortion care.
Doctors prescribe weight loss surgery for fat women who want to become pregnant, which leads to undernourished fetuses and underweight babies. Then the women who had the surgery are much much more likely to die from the surgery and malnutrition. So their children lose their mother.
The children of a fat woman are more likely to be removed from her care by the state because of assumptions that she can't be a good parent.
Lawyers will also use a woman's fatness against her in divorce proceedings to force a less equitable settlement through the threat that a judge will see her as an unfit parent.
Fat rights are reproductive rights.
Information mostly from the book Tipping the Scales of Justice where you can read all about this and many other completely depressing topics about how fat people are legally subject to discrimination.