Doing a greater distance than you have done before has that effect. But the next time you do the distance you have the benefit of some adaptation.
But there are several points worth making.
- It is best not to increase distance more than 10% in one go. Increasing it a bit increases endurance without grinding to a (near) halt. The aim can be to increase the distance you can run at a reasonable pace rather than distance alone.
- Hydration is essential for long runs. The reason is that you dehydrate steadily and when it gets to more than about 2% of bodyweight it slows you down
- Fueling - mainly taking on carbohydrates - avoids some of the slowing down and is beneficial over an hour and increasingly important at 2 hours and beyond. The reason is that glycogen is quite limited in the body and when you run out it's very debilitating! It's called "bonking" by marathon runners. Legs lose all power and you can hardly keep going.
Of course, those who run 2 hour marathons have to take it a bit further than that! It was a major team effort involving multiple companies and experts to get a very talented runner - 31 year old Sebastian Sawe - to sub-2 at London. He has been working with the same coach for 6 years to get him from when he was a 1 hour half marathoner to being a 2 hour marathoner.
To bring this back on topic, most of the thousands of international participants in the London marathon had to fly long distances to get to the start line, but the entry fee included £26 used to buy carbon offsets in order to achieve net zero emissions.

Your jokes are becoming less funny. And you really should put “/jk”, it’s hard to tell what’s a joke and what isn’t, EE.
It’s either a bad joke or an unintelligent thought. He’s losing either way.