It’s hard to tell just by looking at a person whether or not they can hike any distance. It’s not a function of weight or age to be sure. It really appears to be a function of what we casually refer to as lung capacity but also includes heart health. Hiking on level ground is much different than hiking up and down mountains. Even if you have hiked 10 miles on the flat, you may find that your heart starts pounding wildly in your chest on a three mile, very steep hike. This will require you to stop until you can catch your breath and slow your heart rate down. This is not necessarily a problem if you are hiking with a few of your friends. But if you are not in shape and are on a group hike with seasoned hikers, this can be problematic. You will definitely be holding them up. Some groups don’t mind. Some groups do.
If you have not hiked in the mountains with any substantial elevation gain, you should never even start a hike of more than a few miles at first. Keep it under 5 miles. You will need to work your way up to more difficult hikes over a period of time. It could take up to a year for you to get into the kind of shape where 10 miles and 2,000 foot elevation gain does not really phase you. And we are talking the Carolinas. (There are some places in the US where the hikes are much more strenuous than this!) That does not mean you won’t get tired or be slow going up and down. We are not talking speed here. But it does mean that your heart won’t be pounding every time you take an up. I like that old saying: Slow and steady wins the race!
Finally, there is a good reason to take it easy and slow when you are getting into shape to hike the longer, harder trips. You want to enjoy your journey in the mountains. Not hate every step of it. You don’t want it to become a slog and a chore. If you give your body time to become accustomed to hiking with elevation gain over time, your hiking will become much more enjoyable and you will want to keep doing it.
And then think of all the wonderful places you can take on!