My best friend died at 49. I was 49 too.

I remember the weeks after — 137.5 kilos, knowing two things at once. That life was shorter than any of us let ourselves believe. And that if I kept going the way I was, I might not even get the warning Matt never got.

I wasn't lazy. I wasn't weak. I was stuck — heavy, low, and grieving.

Before he died, I made Matt a promise: to do something in his memory people wouldn't believe I could do. When I told a mate I'd run the London Marathon, he laughed. At 137.5 kilos, I understood why.

But I wasn't training to lose weight anymore. I was training to keep my word. And every time a run got hard, I'd talk to Matt and aim for the next lamp post. Then the end of the road. Then the next one.

Five years later: 92 kilos, four marathons, and over £25,000 raised for Macmillan Cancer Support.

I'm 53 now. I'm not a fitness model. I'm a bloke who found the way out and wrote the map down — so the next man doesn't need five years to find it.

That map is Reset 40. For Matt.