How Cronometer’s precision nutrition powered a Toronto runner to a marathon PB

For Toronto runner Tony Wu, better nutrition meant better performance, and he proved just that at last weekend’s Toronto Waterfront Marathon. Chasing a 2027 Boston qualifying time, the 31-year-old shaved 13 seconds off his marathon time, running 3:01:12–thanks to smarter training and a nutrition strategy powered by Canadian‑built nutrition-tracking app, Cronometer.

Wu, originally from Victoria, began running in 2020 and made his debut at the 2024 Ottawa Marathon, finishing in three hours and 14 minutes. This year, he was took on a lofty goal of hitting the 2027 Boston Marathon qualifying standard of two hours and 55 minutes. To make sure he prioritized all aspects of training, he used Cronometer to log meals and track his fuelling throughout his build.

“Cronometer played a big piece in this,” Wu said. “I was able to attack my workouts a lot harder and recover a bit easier because I wasn’t at a deficit every single time.”

On race day, Wu says he was excited, but conditions were far from ideal. “It felt a bit warm during warmup,” he said. “Then my friends began getting fatigued about 5K into the race–that’s not a good sign when you still have to run more than 35 km.” The conditions made pacing difficult, and Wu felt his left quad begin to cramp at around the 15-km mark.

“It was humid and windy, which broke my confidence when I wanted to surge,” he said. “But the crowd support on the race course was unbelievable,” he admitted. “I have never seen the city more alive than on race day. I’m really happy that everybody got to be out there.”

Wu crossed the line six minutes shy of his Boston qualifying standard. “It’s not the outcome I hoped it would to be,” he said. “But I’m really happy with the performance on that day.  In those conditions, very few people I knew had a good day out there, so I felt like one of the lucky ones.”

He says the most difficult part of the 42.2K run was watching some of his friends struggle. “It was hard to see a lot of my friends, who have been training really hard for this race, not having their best day,” he said. “You want to see your friends succeed.”

In contrast, Wu said his favourite moments came at the Parkdale cheer station and through Coronation Park, where he spotted friends in the crowd and bursts of confetti lifted his spirits. And, of course, the finishing stretch stood out most of all. “Just seeing my partner and her friends cheer me on and have their signs out,” he said. “It was really encouraging to have that towards the end.”

Cronometer’s role on race day

Wu credits his resilience and consistency to fuelling smarter with Cronometer. “The app provides an easy way to look back on your training over a long period,” he said. “I used the charts to track my carbohydrate intake, and now I can clearly see I was taking more carbs at the peak of my training block–which led to a solid performance on race day. I can also pinpoint exactly which days I had big workouts because there are spikes in my net carbohydrate intake, which means I did a good job of making sure I was replenishing those energy stores post run.

“Now that I have this data, for the next block, I can do a better job of making sure my caloric intake was more consistent on a day to day basis, as there was quite a large variance throughout the weeks.”

In the final weeks before the marathon, Wu used Cronometer’s data to guide his carb-loading strategy, adjusting his macronutrient targets to increase carbohydrates while reducing fats and proteins. The focus on nutrition gave him confidence on race day, and he says this year’s marathon felt smoother and more controlled than his first.

“I had a more positive mindset leading up to the race,” he said. “The run didn’t hurt as much, even though it was very tough. I feel like a sub-three or a Boston-qualifying time was definitely within grasp, but given the conditions on the day, I felt like that effort was the best I could do.”

His biggest takeaway is that data-driven nutrition matters. “Cronometer is a tool that any athlete could benefit from,” he said. “People want to train like professional athletes or run fast times, but they don’t always do the other things to support those kinds of performances. Nutrition is often overlooked–but it’s a critical part of being an endurance athlete.”