A sixty year old can do all the things a parent needs to do. Your parents were just too fat or lazy or both.
I my opinion as soon as you have kids you give up any right to be a fat lazy unfit slob. At no point does a child deserve to see their parent falling apart and on a million drugs because they refuse to take care of themselves.
Doesn't matter if the parent is 40 or 80. It is now your job to stay as healthy and active as possible until you die.
My grandparents are still healthy well into old age, surrounded by great grandkids. They live with family, but overall are still very independent and the whole family is happier because they're healthy and doing well.
Meanwhile I have other family members who have expressed they worry their parents won't live long enough to see their grandchildren because they're so sick from lifestyle related disease.
I find it disgusting because it causes them so much distress and not having a parent around to guide you through those first years of a new baby is such a hard thing to deal with.
When you pick up the diapers, you also pick up the weights and put the doritos and mountain dew away.
My spouse and I have both agreed that once we agreed to have a family we also agreed to keep ourselves mentally and physically healthy so our kids don't have to spend a single bit of energy worrying about us or feeling we're holding them back. It was great motivation and we're both healthier for it.
Might be a hard stance to take, but I've seen what the alternative can do and it's not pleasant. Especially because for the first ten years you are your child's role model.