In late 2020, I watched The Game Changers on Netflix. I’d been racing triathlons since 2010 — a decade of sprint races, Olympic distances, and 70.3s — and I’d never once questioned what I ate. Meat, dairy, and the standard endurance athlete diet. Pasta the night before a race, eggs in the morning, chicken after long sessions. It worked. I had no reason to change it.
The film triggered the question. Rich Roll’s Finding Ultra confirmed it was achievable. Cow on BBC sealed the decision.
By the end of 2020, I’d decided to run an experiment: switch to a plant-based diet, track the basics in MyFitnessPal, get a blood test done, and see what happened to my racing.
I had real concerns going in. B12 was the obvious one — every endurance athlete forum mentioned it. I worried about hitting calorie targets across a ten-plus-hour training week without dairy and meat anchoring my plate. I wasn’t sure whether I’d lose muscle on plant protein. I treated all three as questions to answer with data, not as reasons to hesitate.
Five years on, the answers are settled. My 70.3 times dropped from around 5h30 in my omnivore days at Castle Chantilly and Les Sables to consistently under five hours. My entire IronMan career has been plant-based: five full-distance finishes between 2022 and 2025, including Challenge Roth in 10h10 — my best ever — and Cascais six months after breaking my collarbone.
This is what actually changed. How I prepared, what surprised me, where The Game Changers got it right, and where it oversold the case. And what plant-based hasn’t solved — because honesty matters more than missionary zeal.

Three sources moved me from “I should probably eat less meat” to “let’s actually try this.” None of them on their own would have done it. Each one did a different job.

The Game Changers came first. Produced by James Cameron and starring Arnold Schwarzenegger and Jackie Chan, it follows MMA fighter James Wilks investigating whether plant-based diets can actually fuel elite performance. Critics have rightly called out its cherry-picking and conflicts of interest, and the science is more nuanced than the film suggests. But that wasn’t really the point for me. I wasn’t watching for proof. I was watching for permission to consider it. The film opened the question I’d never bothered to ask: what if?

The Game Changers showed elite athletes thriving on plants. Finding Ultra showed something more useful: a competitive athlete who’d done it without genetic gifts. Rich Roll was a 40-year-old former Stanford swimmer who’d let his body go, switched to plant-based at midlife, and gone on to complete Ultraman and the Epic5 — five Ironman-distance triathlons across five Hawaiian islands in under a week. The film said it was possible for the genetically gifted. The book showed it was possible for someone like me. Roll’s specific account — his bloods, his training, his honest documentation of what worked — was the bridge between “elite athletes do this” and “I could try this.”

By the time I watched Cow, the BBC documentary by Andrea Arnold, the decision was already mostly made. Four years following the life of one dairy cow named Luma, no commentary, no statistics, no agenda. Where The Game Changers spoke to my brain about performance and Finding Ultra confirmed a competitive athlete could do it, Cow gave me the second reason. The environmental and ethical framing I’d dismissed for years suddenly landed. It was the validator that the experiment didn’t strictly need, but that made it feel right.
Three sources, three different jobs. Trigger the curiosity, confirm the feasibility, and validate the choice.

I’m organised enough to take a switch like this seriously, but I’m not the type to plan everything on a spreadsheet. The way I went about it was more practical than rigorous.
I bought cookbooks before I bought supplements. The food had to work day-to-day before any clever sports nutrition layered on top, and I wasn’t interested in living off pasta and bananas for six months. Rich Roll’s PlantPower Way and a few endurance-focused cookbooks lived on my kitchen counter for the first few months while I figured out how to actually feed myself across breakfasts, recovery meals, race-day fuelling, and the occasional dinner with non-plant-based friends.
I started using MyFitnessPal from the first week. Not obsessively — but enough to spot the obvious gaps. The first month threw up some surprises. Iron and zinc were the easiest to under-hit. Calcium took adjusting once dairy was gone. Calories were never the problem I’d been warned about — eating enough as an endurance athlete on a plant-based diet is genuinely straightforward once you stop fearing carbs.
Blood tests went into the calendar every six months at first, dropping to annual once the first year of results came back clean. Ferritin, vitamin B12, vitamin D, full blood count. I wanted some actual data before drawing conclusions, rather than going off how I felt. The first round in mid-2021 was the one that mattered — everything in normal range, B12 healthy thanks to the supplement, ferritin actually up slightly compared to my omnivore years.
What I’d tell anyone considering the same switch: do a bit of homework first. Buy a couple of cookbooks. Track your intake for the first few weeks just to confirm you’re hitting the basics. Book a blood test six months in. The athletes I see fail at plant-based aren’t failing because plants don’t work. They’re failing because they switched without thinking it through and ended up under-fuelled, under-supplemented, or both. The Iron and B12 piece covers what to track. The supplements piece separates what’s worth taking from what’s marketing.

The first three months were a wash for any meaningful conclusions. I was learning what plant-based even meant for someone training endurance volumes — adjusting recipes, dialling in pre-session fuelling, working out what plant-based recovery looked like in practice. I wouldn’t draw any performance conclusions from that period.
By month four, the daily routine was stabilised. Pre-workout fuelling was the easiest swap — oats with banana and almond butter became my standard pre-session breakfast, and my plant-based pre-workout guide covers what I tested before settling on what works. Hydration changed less than I expected once I figured out the electrolyte gap that comes with cutting out a lot of processed foods — I wrote up the hydration approach I landed on once it was actually working in races.
The bigger surprise was something harder to explain. By mid-2021, on long sessions, I started noticing a feeling I hadn’t had before — like I could just keep going. Not faster. Not stronger. Just a sense that the bottom of the tank wasn’t where it used to be. It reminded me of the rope-climbing scene in The Game Changers, where the NFL player keeps going up the rope long after he should have stopped. I’m not claiming that effect was real for me at the same intensity — I’m a competitive age-group athlete, not a pro. But that feeling of “I could probably do another hour” on a long ride started showing up in training, and I noticed it. Recovery was the other change. I’d assumed the difference would be minor or perhaps slightly worse, given how much I’d relied on whey shakes and chicken in the post-session window. Instead, by mid-2021, I was hitting back-to-back hard days more consistently. I’m cautious about claiming this as a plant-based effect specifically. I was also sleeping more during lockdown, training more consistently, and paying closer attention to nutrition timing than I ever had before. Multiple variables. But the recovery wasn’t worse, which was the bar I’d set.
The hard sessions felt the same. Threshold runs, FTP intervals, race-pace efforts — none of it changed in any way I could detect. My RPE in training felt identical pre- and post-switch, which was both reassuring and slightly anticlimactic. The feeling of extended endurance was the genuine surprise.

My first race after going plant-based was Marlow Fugitive in 2021. A 70.3 on paper, except the Thames swim got pulled at the last minute — water quality wasn’t safe to swim in. So it became a 3K run, 90K bike, then a half-marathon off the bike. Whatever I’d trained for went out the window, and on top of that, I was racing on a diet I’d been following for less than six months.
My fuelling plan was sorted well in advance. I’d swapped my usual gels for plant-based alternatives months earlier and rehearsed the whole nutrition routine in long training sessions. Race week itself was the same prep I’d done a dozen times before — track everything, lay out the kit the night before, eat the same breakfast I’d practised for weeks. The Thames cancellation was a curveball, but the nutrition wasn’t. The actual race went fine. Not a personal best, not a disaster — just a competent age-group performance. The nutrition held. My gut held. I crossed the line at a finish time that, accounting for the unfamiliar format, was completely consistent with what I would have run as an omnivore.
That race taught me something the documentaries hadn’t: race day on a plant-based diet isn’t dramatic. It’s not a triumph. It’s not a struggle. With reasonable preparation, it’s just another race. The drama lives in the months of preparation, not in the four hours of the course.
The full distances followed. IronMan Nice in 2022 was my first IronMan, 11h17 on a course that’s anything but flat. JurassicMan came later that same year, racing the IronMan distance along the Jurassic Coast in the UK — a different beast entirely from a sanctioned IM. Long Course Weekend Wales in 2023 spread the IronMan distance across three days in Tenby, which is its own kind of hard. Challenge Roth in 2024 became my best IronMan: 10h10 on the famously fast Bavarian course. IronMan Cascais in 2025 was the toughest mentally — 11h57 finishing six months after breaking my collarbone, racing in heat that exposed my electrolyte plan in ways British training never had. Five IronMans, five different lessons, all on plants. I’ve written about the race-day fuelling strategy I’ve refined since 2021; the electrolyte balance piece covers what Cascais taught me about racing in heat, and the nutrition brands I actually use are written up there too, with no affiliate deals attached.

This is the section I owed myself when I started writing this.
The Game Changers got a few things right, in my experience. Recovery on a plant-based diet is at least as good as on an omnivore one, provided protein and calories are met. I haven’t had a worse recovery year since 2021, and my 70.3 times tell the cleanest story I’ve got: pre-switch I was running 70.3s around 5h30 at Castle Chantilly and Les Sables. Post-switch I’ve been consistently under five hours. That’s a thirty-minute gain, which is significant at any level. The film’s overall claim that you can race endurance events on plants without compromising performance — that one holds up. In my case it more than holds up.
It also got the inflammation argument broadly right, although the mechanisms are more complicated than the film made out. I notice less general soreness after big training weeks now. Whether that’s the diet, better sleep, age-related adaptation, or some combination, I genuinely couldn’t tell you. I’d recommend my active vs passive recovery piece and recovery foods for what I’ve actually settled on.
What it got wrong, or oversold: plant-based isn’t a one-variable performance shortcut. The film implies that going vegan unlocks athletic gains in isolation, and that’s not how it actually works. My 70.3 improvement was real, but it didn’t arrive in a vacuum. I trained more consistently between 2020 and 2024, slept better once lockdown changed my routine, and got smarter about race execution. The diet was a meaningful factor — a positive one in my case, not a neutral one. But it wasn’t the only factor. The peer-reviewed literature backs the broader picture: when calories and protein are matched, plant-based and omnivore athletes perform comparably, with some evidence for recovery benefits on plants.
The film also seriously oversold the gladiator section, the erection study, and several other pieces of evidence. If you’re considering switching, watch it for the inspiration, but don’t take its claims as scientific consensus.

Five years in, here’s what going plant-based hasn’t fixed.
It hasn’t made me immune to bad sessions, the bonk on a long ride, or the morning where the legs just don’t show up. It hasn’t made me immune to mental fatigue, which I’ve written about separately, nor has it made sleep any less essential. I still need eight hours of sleep, and a poor week of sleep is a poor week of training, regardless of what’s on my plate.
It hasn’t simplified social situations. Race events still cater poorly for plant-based athletes, restaurant menus during away races are still hit or miss, and I’ve eaten more pre-race emergency oat porridges in airport hotels than I’d care to admit. Travelling to a race in continental Europe still requires more planning than my omnivore mates seem to need.
It hasn’t made me a better person. That sounds obvious, but it bears saying because so much plant-based content carries an implicit moral framing. I switched for environmental and curiosity reasons. I’ve stayed because the data on my own racing supports it and I’ve grown to prefer the food. I don’t judge what’s on someone else’s plate.
Plant-based is one decision among many a competitive athlete makes. Training consistency matters more. Sleep matters more. Race-day execution matters more. The diet is a piece of the puzzle, not the puzzle itself.

The argument I trust least in nutrition writing is the one without data. I’ve raced enough since 2021 that the comparison is reasonably honest now
You can see my full results across my race history page — sixteen years of times, distances, and finish positions, with the diet-change line drawn in late 2020. The numbers tell their own story. My 70.3 times pre-switch sat around 5h30. Post-switch, they’ve been consistently under five hours. My entire IronMan career has happened on plants: IronMan Nice in 2022 (11h17), JurassicMan in 2022, Long Course Weekend Wales in 2023, Challenge Roth in 2024 (10h10), and Cascais in 2025 (11h57) with a six-month-old collarbone. The post-switch trend is upward or flat across distances, never downward.
The full Cascais race report covers what worked and what didn’t on the day — racing back from injury changes everything you thought you knew about pacing.
If you’re earlier in your triathlon journey, my first IronMan reflection piece covers the broader lessons that have nothing to do with diet — and most of what gets a first-timer to the line is exactly that, broader than what’s on their plate.

If you’re considering the switch, start with the Iron and B12 guide, then the supplements piece, and then come back here once you’ve spent a few weeks tracking your intake. The nutrition pieces are the technical foundation. This page is the lived experience that tied them together for me.
If you want the racing context — what competitive age-group triathlon actually involves, regardless of diet — the first IronMan piece is a good place to start, and my race history page shows the long view.
I’ll keep updating this piece as the racing evidence accumulates. Five years as a plant-based triathlete, five IronMan finishes, and a thirty-minute 70.3 improvement isn’t nothing — but it isn’t a lifetime either. The next five years will tell us more.