You can if you will it!
I walked last year, 1300km on the Camino de Santiago. BUT I was in awe of a 140kg guy who I met half way and he was going to end up walking further than me.
He is a total legend who changed my mind on what people are capable of doing. They can change and be better.
Get help from people who know how to help, write down your goals, stick them on the wall, break it down into monthly things, weekly things, daily things to do and keep heading in the right direction.
A final point also, when I walked, the guys I walked with who were in their sixties or seventies were all stronger, they had some muscle.
It didn't hit me until a few weeks ago, there were no skinny guys or too big guys in their sixties or seventies who were walking. There was a lesson there for me, get fit, put on some muscle and you will be able to be active into your old age.
Now I look forward to being that fit, annoying old man who is still charging up hills in his sixties giving the young whipper snippers a go.