Does running a marathon make you healthier?

When I first started running over a decade ago, I quickly built up to 2-3k. 5k+ was a little harder. I have flat feet, and it became a challenge to overcome the frequent foot pain I had. Then I invested in good shoes, and built up to the occasional 10k over a few years. Soon, I considered anything below 7k to be a “short run”.

I kept pushing into trail runs, 12-13k regular runs and finally I ran my first half marathon in 2018, about 3 years after I started running regularly. I ran 3 more after that, finishing in the 2:20-2:40 range. The first 3 HMs were extremely exhausting. The stretch after 18k was particularly brutal. Blisters on my feet, heart rate rising, my glutes complaining, I had to summon every bit of willpower to trot-walk-drag my way to the finish line.

2025 was different. I got a bit savvier about my quest for healthspan optimization, and decided to train smarter. I did a lot of strength training and built up my general fitness. And it showed. This was the first time I was able to actually speed up in the last km and sprinted across the finish line. I felt like I could have run longer if I hadn’t done that last burst. For the first time, the brave people who continued onward with their SECOND half marathon to finish their 42.2km didn’t seem absolutely insane.

And yes you guessed it, that’s my new target. I think I can run the full 42.2km this year and I have signed up for it.

Now, we all know running improves cardiorespiratory fitness, which is one of the strongest measurable predictors of longevity; people with high versus low fitness had about half the mortality risk in a 2024 overview of meta-analyses spanning 199 cohort studies. But most of this fitness can be achieved at much lower levels of cardio than running a marathon.

On the other hand, athletes show a higher rate of atrial fibrillation. A 2021 systematic review and meta-analysis found about 2.5 times the odds compared with non-athlete controls, with athletes under 55 at greater risk than those 55 and over. Mixed sports (e.g. soccer, rugby) carried more risk than endurance sports, and none of it says an ordinary recreational runner carries a career athlete’s risk. But still, as we push the system it is reasonable to expect some risk increase.

There is also the background risk of injury. Roughly half of first-time marathoners pick up an injury during training. It usually tends to be minor but roughly 1 in 10 get a serious enough injury to keep them from starting or finishing (Toresdahl et al., 2021). It is also hard to maintain muscle mass with that much running. You might have heard stories about marathoners getting cardiac arrests, but that’s exceedingly rare. The risk is higher while you are actually running the marathon, but it is still tiny - only about 1 in 100,000.

So does running a marathon make you healthier, or are you worse off for attempting it? I spoke to a doctor friend trained in sports medicine, and he advised me that if planned properly, most of the downside risk can be substantially reduced — leaving a small net upside (I might lose a little weight and slightly improve my cardiovascular markers) and a temporary downside that can be reclaimed.

I will document my journey, along with my misconceptions and how I evaluated the risks and trade-offs. I hope to illustrate the nuances that matter when fine-tuning a programme, how my own preferences and lifestyle get in the way. I will also measure my VO2max to see if it improved my overall cardio-respiratory fitness.

Follow my journey on https://marathonlongevity.run