The Spaniard, who is currently 42, has already defied doubters who reckoned that F1 drivers would be long past their prime once they were out of their thirties.
Now, as he ponders his next steps in F1 with his current Aston Martin contract coming to an end later this year, the two-time world champion says a change of diet and a new approach to fitness has led him to conclude that he has a lot of racing left in him.
That belief has been triggered by his recent annual medical checks at a clinic, which pointed to him not only having unexpectedly arrested a decline that had been spotted in recent years but now being in the best shape ever.
"We usually do the same tests," he said. "The first part we do in the Alps, in Italy, in the mountains.
"We have historical data of my body's cardio performance in one, two and five kilometres, in a resting state, in a thousand and one tests of fat or muscle, of reaction with the lights, as well as maximums from the gym with weights.
"While in some tests over the last five or six years, there was a minimal drop in performance, especially in terms of muscle, because, from the age of 30 or 35, you lose a little muscle. This year, we have been able to recover it to maximum levels. And this has been partly due to nutrition, which has changed.
"We tried to gain a bit of muscle to compensate for the age factor, without losing reactivity or endurance in cardio. These were surprising results, and I think very positive."
Alonso spoke several times during a pre-launch media briefing at the weekend about the benefit that will come from Aston Martin now having a nutritionist on board.
He says this has "changed a little bit our way of seeing things and prepare the body" as he hinted at moving more towards a vegetarian diet.
"There are many things that they know in terms of explaining better, that it changes maybe more into a plant-based diet," he explained.
"Maybe not completely strict, but into that route, to try to find a little bit more energy from the food that you eat, and a little bit more from your reserve as well in your body, and try to have more endurance from there."
Another area Alonso has focused on is ensuring that he does not get run down away from grand prix weekends. He has talked of having a better winter with fewer promotional events.
"I have trained more calmly, although it is true that last year the season ended earlier than usual, and I had more time to train, but it has been a winter with much more time for me than I had before.
"I always had something to do during the winter, either I had publicity events or I changed teams and we had to do things at the factory. This time I have had time for myself, to drive other cars, and that has helped me to come into this pre-season in the best shape of my life."
And there is a new approach to dealing with travel through 2024 too, as he aims to minimise time away from home.
"I think we will have to travel more efficiently and we have to spend the right time in the right places," he said.
"I think every one of us is different but, in my case, for this calendar, I will try to have a little bit less time in the long races in that city, in that racetrack.
"So, Japan, Australia, China, I will try to fight jet lag in a different way, and not going super early into that country, because that keeps accumulating days away from home. And the energy and the batteries they keep draining throughout the season."
All these factors coming together, allied with the results of his winter fitness tests, have left Alonso sure that he could race on for many years.
"A few years ago, I would say that maybe 40 to 41 was the limit," he said when asked about how long he reckoned he could go on.
"Now, after I saw myself last year, motivated and performing well, I was thinking maybe that I can keep racing a few more years.
"This winter, I've been exceeding a little bit the expectations in terms of all the physical tests and everything that I did, so I will say that if you are motivated, and if you want to commit, you can drive maybe until 48 or 49, or whatever, or even 50.
"But, at the same time, you have to give up everything in life. Formula 1 needs total dedication. This is my 24th season or whatever in F1 and I gave my life for 24 years to this sport, which I'm happy and I'm okay with that.
"I can keep doing it for a few more years. But I don't know if I will be racing until 50, with such a demanding calendar and things like that. Not for the abilities, but because there are other things in life that I'm curious about."
Additional reporting by Mario Galan
