Middle aged fat guy here, but used to walk for exercise. Decent pace, about 5km per day. But one day, just after I started out, out of nowhere, I couldn’t seem to get enough oxygen. Well, it felt like I could get a full breath, but nothing was happening with it.

I stopped until I could ‘get my breath back’, then continued my walk with no problems.

Next time I went to the doctor, I told him about it. Various tests, etc. Turned out to be Atrial Fibrillation. It’s where the top half of your heart says, “Nah. Don’t feel like pumping blood today. You can just have it trickle down to the lower chamber”. Lower chamber fervently grabs what oxygenated blood it can to pump to the rest of the body.

Fortunately, able to be managed in my instance, with medication (though I did have a ‘cardioversion’, where they stop your heart for a beat to ‘reset’ it).

Given the severity it can take in others, I feel very fortunate mine is manageable.

Your friend might not have that, but they might. It’s an easy couple of tests to find out.

I’m still fat, but I’m still walking, and more often than not, I realise how good feeling like I’m getting enough oxygen is. Which is a nice little boost.