App EXCLUSIVE: Interview with Brock - Fuel My Run app
29 Jan 2026 · 30 min
Mark Kennedy, an exercise scientist from Toronto, explains how strategic carbohydrate fueling cut 40 minutes off his marathon time. He recommends 60 grams per hour for marathons and describes his Fuel My Run app, which sends timed reminders to eat gels and sports drinks during races.
Questions this episode answers
Feb 1, 2014
Healthenomics
May 4, 2014
First marathon in 2008; second marathon in 2013
First marathon ~4:35; second marathon ~3:55
Chapters
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Cheers.
Nice. Cheers.
Hello, everybody. Just having a little sip here. Hey, it's Brock here filling in for Ben Greenfield while he's off in Israel. He actually did Israman. I think it's called the triathlon in Israel. That's apparently one of the hardest in the world. I don't know how he did. I guess he finished and I believe his last words or as he crossed the finish line, he said something like, that was hard, which I don't think I've ever heard him say. He usually is like goofing it up and waving his arms and sort of cheering on the crowd or egging on the crowd when he crosses a finish line. So it must have been a tough day for him. But anyway, I'm here today with Mark Kennedy. We're sitting here in Toronto, Ontario, in the same room enjoying a Muskoka beer. We're fueling our podcast because today we're going to talk about Fuel my Run and, and how to. How to go about that using a new app. But we'll get to the app a little bit later. Mark, welcome to the show.
Thanks, Brock. And cheers. Happy New Year.
When you hear awkward long silences, it's because we're sipping our. Our beer.
It is Friday.
It's Friday.
Not sure when this will air, but it is a Friday for us, so.
It'S a Friday for us.
We deserve it.
Absolutely. So you've got a new app that just came out for the iPhone? Well, not just. It's been out for a little while now. I've got a chance to give it a try a couple of times. But before we tell the people all about that, let's hear about you.
Sure. So I am. Well, I'll start with sort of my exercise science background first and what how I got into running and all that. But I'm a former kinesiologist. I studied kinesiology at Simon Fraser University in Vancouver.
Cool.
I grew up on the west coast in Victoria. I did work in the exercise rehabilitation field for a little while doing exercise rehab for injured workers. I worked with some athletes. I also worked as a personal trainer for a little while, but actually the physio Clinic I worked at, I think my second job at university. They ended up laying off a bunch of people. It was poorly managed and so I got a little bit disgruntled from that. And this is around the time, probably 1999, 2000ish, sort of when the Internet boom was happening and I was getting interested in the stock markets and stuff following that as well. So. Wow. When I got laid off, I thought, oh, this is a good opportunity to explore other.
Change directions.
Yeah. Explore other options. So I, I did some other courses, some. Some finance courses as such, and ended up getting a job with Merrill lynch in Victoria, bc. And so I've been working in the, the finance industry ever since. But I've always had a huge passion for exercise science and health and fitness and running and I've kept that passion alive through just my own training and probably about three, four actually it's going, it's coming up. Five years ago, I started a health and fitness blog where I, I write and I interview various health and fitness experts and I, I have a podcast as well where I interview people. So.
Oh, yeah, what's, what's that called?
The blog is called Healthenomics. Healthenomics, yeah.
Not Healthenomics, but Healthenomics.
Yeah.
I made that mistake. I went to the wrong website the other day. I was like, wait a second, this.
Doesn'T make any sense. Yeah, it's kind of a confusing name. And I, I've always thought about changing it. No, I like it. It's just.
You just have to make sure to.
Put the Y instead of the E. Yeah, exactly. I think. I don't know how I got the idea for the name. I think it came from like, Freakonomics. And, you know, that book was popular and, and I read in a magazine someone talking about beautynomics and the whole makeup industry. I'm like, oh, what about Healthy Nomics? So that was the name. So that's an outlet for me to just stay in tune with what's happening in the health and fitness industry. And that's sort of how I became to follow yourself and Brock's or, sorry, Ben's podcast and website and, and back to the running, I guess. I've been running for about 15 years. I've run, I just signed up for my sixth half marathon, which would be on May 4, 2014, and I've run two marathons. One in Dublin, Ireland, when my wife and I were living in the uk. And then the second one was last year, Toronto. Good life.
So you've been running for a long time? But haven't done a lot of. A lot of racing.
Yeah, exactly. I've always ran, but I've. Haven't necessarily done, well, a ton of, like, long races. I. Every year I kind of do one or two, you know, 10k type things. But it wasn't probably until probably seven, eight years ago that I'm like, oh, let's try a half marathon. And all my friends thought I was nuts, or. Well, they still do, actually, but I. You know, the first half. Even the first half marathon, I'm like, wow, that was really hard and horrible, and I never want to do that again. And then. Then you do another one, then you do another one, Then you're like, maybe I should do a full. And now I'm done.
I did the full first, but I had the same reaction as I crossed the finish line. I believe I said, that was the worst thing I've ever done in my life. I'm never doing that again kind of thing. And then I think it was not even an hour later that I said something like, next time, I'm gonna train harder on my heels or next time. And it's like, doesn't take long to sort of get over that initial. That was really hard. That sucked.
Yeah. You can see how people get addicted because. Yeah.
So the audience that we talk to here on Ben Greenfield Fitness is. They're probably thinking, that. That sounds like your friends were like, that's crazy. What are you doing running marathons? But all these people are like, why wouldn't you run a marathon? So it really comes down to the audience that you're. That you're talking to. It's kind of.
Well, exactly. I mean, now that I've done a few more races over the past, you know, three, four years, I've met more runners, you know, like yourself. And, you know, I'm talking. They're like, how many marathons you done? I'm like, two. And how many have you done? They're like, oh, 15. Actually. I interviewed a guy on my podcast who has done 300 marathons in 300 different countries. Wow. And he was trying to run. He may. May have done it now. His name's John Mad Dog Wallace, but he's actually. I think he's run a marathon in every country that has sort of a sanctioned, official marathon. He's got some crazy stories, and one of them was actually running a. Like, a marathon in Israel. And. But, yeah, he's. He's actually run a marathon in every state as well in the US and he said back in the Day he said the.
The Marathon Maniacs.
Yeah, yeah. And back in the day he said he actually some weekends he would run a marathon on a Saturday in one state and then drive to another state and run another one the next day.
Geez, that's dedication. I thought like when you, when we first started talking about this, I actually keep a. There's a hidden webpage on, on my website where I keep all my finishing times and keep a log of all the races I've done. And I've just hit 65. I've done 65 races and I started racing in 2007, I think. So it hasn't been that long of racking up all those. But that's nothing.
That's a lot of races.
300 in 300 different countries.
Yeah, that's nuts.
That's insane. But anyway, so you've done a few races and I gather from what you've said about the app and what probably drove you to develop this app was maybe your fueling didn't go quite right. Well, possibly the app is called Fuel My Run if you didn't catch that at the beginning.
Although it's funny story, I didn't realize that my fueling didn't go right until probably See, I ran my first marathon in 2008 and I ran my second in 2013. It probably took me four years to realize that my fueling didn't go right in my first marathon.
Well, so you just thought it was just a tough run?
I just thought that the marathon was brutal, it was brutally hard, it was long. I thought maybe I didn't train enough. And I mean, I think you can always figure out ways you could have trained better. Yeah, and it was my first, I was a rookie so I didn't really know what I was getting myself into. But I actually, as I was training for my second marathon, I listened to this podcast with coach Jay Johnson. I'm not sure if you're familiar with him.
No, I'm not, no.
He does some work with Nike and I think he works with some other athletes out of Colorado. Anyways, a well respected running coach in the States and he has a podcast where he interviewed Dr. Trent Stellingworth who is a nutritional scientist out of the Pacific Sport institute in Victoria, B.C. and he works with a lot of Canada's top marathoners and other track and field athletes. So I listened to this talk and it was all about fueling and he's talking about how many grams of carbs per hour you should be consuming.
Yeah.
And I'm listening and I'm listening. And then I had to pause the podcast, and I just had this epiphany is like, holy cow. I didn't take in probably a third or even a quarter of what he's recommending.
Did you even know? Like, did you even do the math or spend any time thinking about what you were taking in or how much you were taking in?
No.
Yeah, I didn't either. For my first.
Yeah. My first. All I knew, I'd heard about bonking and hitting the wall. Yeah. And so the first aid station I carried around, they're handing out bottles of Lucas Aid, which is. It's like Gatorade over in the uk. And so I had some, and then I grabbed another bottle and I held on to it with dear life for the rest of the race. My wife was like, why are you running with a bottle? And I was like, it was like my lifeline.
So you didn't have any other fuel on you that was. You just got it from the aid station?
I just got my fuel from the aid stations, and I relied on water and essentially Gatorade for the whole race.
Wow. So if they hadn't had anything on the. On the course, you would have been screwed?
Well, I knew they had. Oh, okay. I knew they had sport drink. Okay.
So I was. So you weren't just completely like, oh.
Yeah, no, I was so I. I knew I had to take in something, so I just relied on the water and sport drink, but didn't calculate anything, didn't know exactly the quantity I should be taking. And I was. I just knew, like, don't hit the wall. Make sure you take in some. Some carbohydrates. Yeah. And, boy, was I ever naive.
I don't think that's unusual. Like, I did the same thing. Not even just my first race, but probably my first 10. It was just very haphazard, like, oh, okay. Last time I was. Maybe I hit the wall. Maybe I was just tired. I don't know. I'll try eating more this time. And then somebody said, oh, have you tried these Sharkies? And, like, sure, I'll give those a try. And, yeah, like, just sort of fumbling my way through it. I had no idea. Like. Like, you listening to that podcast of there's actually a science behind how much carbohydrate or how much fat or how much liquid in a. In a scientific setting anyway, that you should have, and you should probably be getting around that number. Maybe not exactly that number, but there's. There is some science behind it.
Yeah, exactly. And yeah. Going back to my Dublin race. I got to the 31km mark, and my wife was waiting for me there, and she saw me and she's like, are you okay? And I was like, not really. She said, my face.
Are you still running or are you walking?
I was still running, but the last. Probably the last 9k, I was alternating between running and walking. Yeah. And it was so. It was so painful. Not physically painful, but just painful, like, why am I walking? But I just. I was. I was just done. I had no energy. My wife said I looked like crap. And, you know, I finished the race. And I thought, wow, that was really hard. And. But I just thought maybe I could have trained better. And I didn't know. I didn't feel properly at all. So, as I said up until I sent this podcast, and then a light switched off. And then for my training, for my second marathon the next day, I had a spreadsheet and I was calculating. I was just geeking out.
Extreme.
Yeah, exactly. And that's my personality. Once I learn about something, I'm like, I am all over it. And so I totally geeked out. I had a spreadsheet. I was practicing my fueling. I tried different fuels. I was like. I had my brother acting as a backup fuel station. So he was meeting me at two points in the race. Should I have dropped some of my fuel I was carrying? He had backup. So, like, I had this bulletproof plan for fueling, and it helped, I bet. Yeah, it's.
That's a huge advantage. Fueling at all was probably. Never mind. Like, having the spreadsheet and all that kind of stuff was probably a huge advantage. Well, not probably. It was a huge advantage.
It was. Did you.
Did that show up in your numbers? Did you make any. Any huge leaps in. In times?
It did. I saw my wife again at kilometer around the same point. She saw me in dublin around the 30, 31 kilometer mark, and she said that I looked a hundred times better. I had color in my. In my face. I had a bit more balance in my step. I was running at my normal pace.
Yeah.
Had a smile on my face. And she's like, it was just like night and day. Like, you were a different person at that same point in the race. And I felt much better. And it trans. Transformed into my times as well. I finished the race in under four hours, which was my goal. My first one, I think I was 4, 35. And this one, I ran 355, so. Wow. It was a huge PB for me and. And so much so that like, you know, after the race, you know, before I was like, I'm never doing this again or after this race, I'm like, I can do better within like 10 minutes. So I just had, it was just a much more pleasant experience. Um, and I have to attribute a lot of it to obviously the training I put in, but a lot of it to the fueling as well. I took the fueling just as seriously as I took my running.
Yeah, well, and, and we know through science and through trial and error that your, your fueling plan is as important as your training plan and sometimes even more so. Like the longer the race, the, the more the fueling needs to be planned out. Okay, so when you were, when you were creating your spreadsheets, what kind of did you do A bunch of research? Obviously you found some, some people who had done some studies. How did you calculate what you were going to take in?
Personally, as I said, I listened to that podcast with coach Jay Johnson and the current research was sort of stating that you should aim to take in 60 grams of carbs per hour for a marathon. Some can't take in that much. They'll have a lot of trouble taking that much and others can take in more up towards 90. So I always had 60 is sort of my, my goal. And so within my spreadsheet, I, I, I, I was decided on the fuel I was using. I practice using certain different types of fuels a few times on a run. So I finally locked into the, the fuel type I liked and, and then I started, I took out the carbohydrate content within that fuel. I used cliff blocks. Which are those, those are little gummies. Yeah.
Things.
Yeah, I never really was keen on the gels and I was a big fan of like gummy bears and wine gums. So it's like, why this is genius. Why wouldn't it gives you something to.
Chew too, like, yeah. Satisfying chew feeling.
Yeah. So I, I like those. And they, they worked well for me. So I calculated how many of those little guys I should be taking to get approximately 15 grams of carbs per 15 minutes, which would get me to about 60 per hour. But also I was alternating between sports drink and the, the cliff block choose. So anyway, so I calculated it all and I also calculated where the fueling stations were within my race. Nice. So I really practiced based on what my race was.
So was it a time based thing or a distance based or a combination of both?
It was a combination of both. Um, it actually worked out really well cause I was basically fueling every 15 minutes and I was running, it worked out with my pace that I was pretty much hitting a fuel station around every 15 to 18 minutes. So it actually worked out really well. But I know, you know, different races have different distances between their fueling stations. I'm sure you've been to some where they're spread out a lot more.
Sometimes it's like they're a whole bunch at the beginning of the race and then they all just sort of thin out for some reason or, or the reverse. There's none in the beginning of the race and then they just hit you with them all at the end.
Yeah, and the crazy thing too is I found most of the big races only offer gels at around the. I think it's like the 20 mile mark or something or.
Yeah, 30, 32 kilometer, 20 miles, which.
Is almost like the worst time because at that that's the point where you're going to be crashing. So like they should really be giving those out. You know, I know it's probably money is the issue. Like they don't want to give it all these free gels, but they should really be giving those out at the beginning, beginning of the race and then by the end, you know, you know, don't get them out the end. Give them out the beginning and the mid part of the race.
Yeah, yeah. There's a lot of theories about that whether you should like fuel your stomach is still able to digest everything and get, get it into your system and then basically like by the end it's all just guts and glory anyway.
Yeah, exactly. So. So yeah, I had my spreadsheet and so I had. And I had basically memorized, you know, every. I was alternating fuel stations between taking sports drink and then the next fuel station I would take my chews and some water and I just kept doing that throughout the whole race and yeah, it worked well for me. Awesome.
Well, so I guess that is probably, I'm guessing why you decided that you needed to make an. An app for this. Not not only for, for yourself but to, to help your fellow man and get their, their fueling nailed down.
Yeah, I know, exactly.
So the fuel My run app is the is. Well, basically from what I've. I've played with it a little bit, but why don't you sort of fill in the people. You'll probably do a better job of explaining it than I will, of course.
Sure. Yeah, it's. It's basically I guess the app that I wish I had had in my training for my second marathon.
So you didn't have to carry a laptop with Excel spreadsheet on it while you were.
Yeah, pretty much. That gets heavy. It was like wearing a weighted vest. But, yeah, I figured, like, wow, if I. If I got so much benefit from my fueling, there's got to be other people out there like me, you know, in 2008, who had no idea what I was doing. There's got to be some other people where this would help them. And it would take a lot of the guessing. And fueling can be, you know, come across as quite complex as well.
Yeah.
You know, if you don't have any math. Yeah, it's a lot of math. And if you don't have a background and nutrition or science, I could. It could be intimidating. I mean, I. I studied kinesiology, and even at first I was kind of like, well, this sounds pretty intense, like calculating all these grams of carbs per hour. And so I thought, there's got to be a way to sort of dumb it down, make it a bit easier and a bit more friendly for sort of those newer half marathoners and newer marathoners to approach their fueling and just to give them a. A chance to have a more enjoyable, successful race.
Yeah, well, just keeping it simple is always the goal of anybody, really. Like, most of us are doing this as a hobby. We don't want to spend our entire lives figuring it all out. I mean, there are a lot of us with a type personalities, too, that do want to spend all that time just sort of nailing it all down. But I think from what I've been playing with the app, it sort of allows for both.
Yeah, exactly. So I designed the app to be as simple as possible, and like any apps, it's going to be an ongoing process. There'll be tweaks and stuff as we go along, and I get a bit more feedback. But I wanted the app to be super simple, and I wanted the app to be able to hold someone's hand, basically, who was a newbie to fueling. So with that, I. I developed two sort of starter plans. One for the half marathon distance, where you'd get 30 grams of carbs per hour, and then for the full marathon distance, you'll get 60 grams of carbs per hour. So that's for people who are just starting out, and then, yeah, that's just.
A good place to start. If you don't know what else to do, where to start. You just sort of turn that on and give it a shot.
Give it a shot.
See how your body reacts to it in. In a training run, not necessarily in a. In a race.
Yeah, don't. Please don't do this in a race. Like, this is for your. For your training and your practice. But that's the idea. And if you find out that, wow, from training for half and, you know, 30 grams initially is really tough, like my stomach felt off, then by all means, like, ease off. And at the end of your run, there's an opportunity for you to rate how your run went and add some notes as well. So that's going to act as sort of a diary for you. So your next run, you'll look back and you go, okay, last time, you know, I took them out, took in this amount of fuel and this fuel type. So this time I'm going to try this. So just provides you with a diary where you can go back and you can use trial and error to your.
Benefit, when it's also tracking your distance, your pace, your. Your route. And you can actually sync it up with what was a Runkeeper.
Correct. It's right now. It calculates your distance, your time and your pace. It doesn't track your route now with any mapping capabilities. However, I'm hoping to add that sometime soon. It does also sync with runkeeper. So I know that Runkeeper is quite a popular running app, and it's a great one. It's an app that I like to use. So just to address some, you know, initial objections from people I know they're not going to discover, come and use this app as their only sort of running app or running tool. So it syncs up with runkeeper, and I'm actually adding, hopefully soon Map my run and a couple other sort of the major ones. So.
Cool.
So a lot of people who use apps, and I realize not everyone likes to use apps when they're running. The purists will be just shaking their head right now going, I use a Garmin, nothing else. And. And I get that. I mean, this app perhaps is not for you.
Yeah, I think we probably lost those people at the beginning of this.
This podcast. Yeah, exactly.
Against this sort of idea.
Yeah.
But I think there are a lot of people out there who don't know where to start, don't know what to do, and just need some guidance. And what I liked about this is, like, I've been doing this a long time. I do have my own fueling plan, but I don't necessarily do a good job of sticking to it. So there was. There's one part of the app where you can actually do your Custom plan. And that's the, that's the part that I wanted to talk about, especially for our audience, because there's a lot of people out there, especially people who are fans of this show, that aren't doing the gels, they aren't doing the goos, they're not doing the, the Gatorades and all that kind of stuff. They're fueling with more real food sources. They're fueling with like, you can superstarch, maybe even like coconut butter, that kind of stuff. So they don't necessarily want to be locked into a certain amount of carbohydrate. They have a plan. But you're. The app allows for that. You can add your custom plan.
Yeah.
So you can, like, for somebody like me who's using almonds and dates and some coconut butter, I can just set these reminders to go off at distances or times.
Exactly. It sort of lets you rely a bit more on science and precision without having to think about it. So before, you know, for that type of runner who wants to do their own plan before your run, you can go in and set your fueling reminders for either a food or gel or a drink at different time intervals or distances. So you can really simulate your up and coming race as well. So if you know exactly where your aid stations are and you want to fuel at those aid stations, you can go in the app and program your reminders to be specifically right when you hit that distance or right when you hit that time. And that way you've, you know, you've really simulated your race to the best of your ability. Yeah.
So then, you know, if you, if you've only got two gels with your, maybe you need to bring two or three gels because you're going to hit those aid stations, but they're not going to be when you need them.
Exactly.
Kind of thing. So what are the. In the app, when you first downloaded it actually comes with a few different fuel sources programmed in. So you can say, I want to use this and this. What have you got in there right now?
Right now I've got.
And this is not an endorsement for any of these products. This is just you just.
No, not by any means.
Just like the more popular ones.
Yeah, I've got more. The most of the popular ones and many, many of the sports sort of gels and drinks that are offered at the big races. So you see your Gatorades, your cliff gels, your hammer gels, your power gel, Goos, there's a couple other ones which are escaping right now, but it's. It's sort of more of the mainstream ones.
Yeah.
I do plan to add actually some real food sources. Excellent for up and coming updates to the app, including the. The superstars, which I know yourself and Ben are big fans of.
Yeah.
Something a lot of our.
A lot of the people who listen to this podcast are really getting on board with that. With that sort of fueling as well.
Yeah, it's great. So I want to have as many fuels in there as, you know, people use. So it's really like there's sort of no excuse for anyone who's like, oh, my fuel's not in here. It's not going to track my data accurately, but I'm welcome to feedback as well if there's a fuel. If someone does decide they want to try it out and you see that your fuel is not in there, just send me an email and I'm happy to add it.
Cool. Yeah. And where actually can they find this? Where can they find you and the information about the app?
There's a website for the app and it's fuelmyrunapp.com or you can just go to itunes and I should make that known as well. It's just available for iPhone right now. And again, I know there's this whole other world that uses Android and BlackBerry. BlackBerry, sorry, BlackBerry.
They don't apologize to them. It's their own fault.
Hey, we're Canadian. We got it. Yeah. But I hope to have an Android version in the spring. But just, just go to itunes and do a search for Fuel my run and, and you'll be able to find it.
We'll make sure to put some links in the show notes too, so you can just. On the, on the Ben Greenfield fitness app, he'll be able to click on the links or go to the website and, and look at the show notes and we'll make sure to have your website and we'll put the Healthonomics and, and the itunes link as well.
That's great.
You'll be able to find. Find Mark all over the place.
Yeah. And by all means, if anyone downloads it and they have any feedback, I really want to get like, you know, real runners using and abusing the app and testing it out and yeah, just give me any feedback you have, positive or negative. I want to make it sort of the best app it can be to really help runners run to their best.
Cool. I, I think that is a good goal and it's a good, good note to, to leave off on. So thanks for coming by and and thanks for bringing beers too. This is great.
Hey, don't forget a podcast on a Friday night.
Visit BenGreenfieldFitness.com for even more cutting edge fitness, nutrition and performance advice.
It.
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