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KEY TAKEAWAYS
High-fat, low-carb nearly tanked my training, my mood, and my relationships; going back to a high-carb approach plus a realistic body-weight target flipped everything—energy, consistency, and performance.
For busy athletes, “minimum effective dose” training works when you nail fuelling: a smart carb-load, >100 g/h carbs on race day, and a few well-chosen supplements beat volume you can’t recover from.
The study that (nearly) broke me
I signed up for a high-fat, low-carb study because I wanted fresh data—DEXA, RMR, VO₂max—and a new stimulus. What I got was a masterclass in what doesn’t work for me. Yes, I leaned out quickly. No, I couldn’t hit high-intensity sessions. My HRV hit the floor (low 20s ms), resting heart rate climbed, I picked up a couple of colds, and I turned into the irritable version of myself nobody wants around a dinner table, let alone at home with a pregnant wife and two kids. Calories were matched to my normal intake—the only real switch was macronutrients—but I couldn’t finish the hard sets. Could I have “adapted” with more weeks? Maybe. Did I want to endure seven more weeks of zombie-legs, grumpiness, and mediocre training with a startup and young family in tow? Absolutely not.
If you thrive on high-fat, power to you. I didn’t. And given the task at hand—running a sub-3 on a rolling Sydney course—my philosophy (and Fuelin’s) is simple: carbs are a performance tool. I went back.
What the testing told me—and why it mattered
The lab work provided blunt honesty. My lactate threshold heart rate hovered around 155 bpm and my threshold pace was ~4:21/km. To go sub-3, I needed ~4:16/km. That’s close enough to be tantalising, and far enough that every decision—sleep, stress, fuelling, caffeine, shoe choice, the whole circus—would matter. The high-fat phase didn’t just fail to move my threshold; it made quality work feel impossible. When I reverted to carbs, intensity came back online almost immediately.
Minimum effective dose training (for real life)
Here’s the bit that’ll make some mileage purists wince: over my 13-week build I averaged roughly 6 hours of total training per week. Running time actually dropped from the previous year (~3.6 h/week to <3 h/week), but I added low-impact aerobic time on the bike—about 600+ km across the block. That extra cycling was the quiet hero: it let me keep building the engine on days I didn’t want (or couldn’t afford) the pounding of another run. Swimming? Let’s just say my 13-week total wouldn’t impress a toddler swim class and leave it there.
The quality run structure was simple: one race-pace session building duration, one interval set mid-week, one progressive long run with race-pace at the back end. That’s it. Not fancy—just consistent. The lesson: if your life is busy, you can’t fake volume. Use the bike for low-impact aerobic load, protect the key run sessions, and spend your discipline points on fuelling and recovery.
Ditching the scale obsession (and running happier)
For months I had Jan Frodeno’s old “seconds per kilo” mantra rattling in my skull. It seduces you into thinking the path to speed is paved with missed desserts. Six weeks out I dropped the fantasy. I set Fuelin to maintenance at ~81–82 kg, stopped trying to “win” the scale, and focused on arriving well-fuelled. I toed the line at ~84.5 kg—heavier than I’d planned—and ran better. Surprise: sleeping, hitting sessions, and not hating life beats being a gaunt zombie fantasising about raisin toast.
The carb-load: going bigger (and smarter)
Historically I’ve sat near 8 g/kg in the final 24–36 h. This time I pushed 10–11 g/kg. Yes, there was rice. No, it wasn’t Instagram pretty. But I felt springy. And we’ve been building a more nuanced carb-load algorithm inside Fuelin with Dr. Alan McCubbin—one that uses a broader set of inputs so lighter, very fast athletes and heavier, still-building athletes get equally appropriate targets. Two practical tweaks: I lowered protein (to ~1.5–1.6 g/kg) and fat during the load to limit fullness and GI drag. More carbs, less “gut brick.”
The supplement stack (no fairy dust, just useful tools)
Creatine monohydrate: 5 g/day, stayed on it the whole block. Yes, you might carry a touch more water. No, it didn’t slow me down. I feel better on it—stronger, more resilient.
Beta-alanine: 6.4 g/day for 12 weeks. I take it at night to avoid the face-tingles and pressure-head. On a hilly course with surges, that extra intracellular buffering helps.
Sodium bicarbonate: I trialled the gel format (not mid-race—just in testing). It worked in a 5 km hit-out but I didn’t trust it for 42.2 km and Sydney’s rollers. Risk > reward this time.
“Plasmaide” / French maritime pine bark extract: I tested six doses/gels in race week. Mechanistically it’s in the nitric-oxide conversation (different pathway to dietary nitrate). Did I feel great? Yes—but I’d also carbohydrate-loaded like a champ. Verdict: interesting, more research and experience with this product required. The Norwegians swear by it. maybe they know something the rest of the world doesn't?
Simple rule I usually preach (and broke, a little): nothing new on race day. If you’re not practised with it, don’t gamble.
Race-morning breakfast: lighter on fat and protein, heavy on carbs
I’ve progressively cut race-morning fat and protein. The goal is topping up liver glycogen and starting light, not winning a brunch contest. I used a PF90 gel, a Maurten 320 drink mix, and thick café-style raisin toast with a modest scrape of butter—about 200–210 g of carbs within 2–2.5 hours of the gun. Caffeine came from two caffeinated gels (two ~60 min) and then another normal gel pre-start, ~15 min.
NOTE: Full disclosure: the caffeinated gels still makes me gag. At 4 km I had a small vomit—nothing dramatic, just annoying. Enough for my running partner, Jack Musgrove to think he had picked a donkey to run with. His words "I thought it was going to be a long day for you, mate!" Thank fully it was a short term impact. Coffee works brilliantly for me; some caffeinated gels don’t. Note to self: refine the delivery, not the dose.
The plan on course: aim high on carbs, respect fluids, time the caffeine
I carried a 500 ml bottle with Maurten 320 (≈80 g) and finished it early (40 mins), then rotated M100/M160 and PF90 gels. Average intake: ~105 g of carbohydrate per hour across the race. That’s aggressive—yet it suited me. My sweat rate in those temps is ~1.6 L/h, so I chased every aid station for water to keep the hydration on pointand limit the cardiac drift you get when plasma volume falls. Caffeine totaled ~500 mg by the finish (front-loaded, then a final caffeinated gel ~30 minutes from home when the wheels started wobbling). For hotter races I’d preload fluids even harder and carry two smaller bottles to make sipping easier.
Did it “work”? I ran my fastest splits inside the marathon (yes: new 5 km/10 km/half-marathon bests en route), then inevitably paid some tax late. But I never faultered (maybe a tiny hill section at 39kms that required a short walk), and that was the difference between a good day and a death march.
The recovery reality (science meets real life)
I practiced what I preach post-race. Within an hour I had a shaker bomb: ~50 g whey protein isolate (True Protein Australia), 20 g creatine monohydrate (a one-off big dose), ~170 g of carbs (M320 drink mix), and 2,000 mg tart cherry concentrate. Then I practiced what I also preach: live a little. Strong flat white. Two pints. A Tommy’s margarita. Cheeseburger and fries. Twenty minutes of easy spinning to flush the quads. Pizza for dinner. Omega-3s before bed. It’s not either/or; it’s both/and. Refill the tank, then celebrate like a human.
The head game: why trumped what
My “why” mattered. When it was dark and cold and the alarm felt like an insult, I said out loud, “Do it for Jack.” Our eldest has a serious genetic condition called SCN2a. I didn’t raise a dollar in this race—I will for the bigger gene-therapy push we’re building—but I ran with him in mind. When you choose a meaning bigger than ego and a six-pack, the results write themselves.
What I’d change next time
Volume: Reality check when reviewing total hours is taht I need to do more volume if I am to have a realistic shot at cracking sub 3. Not crazy amounts more, smarter volume and some more speed work.
Fluids: experiment with two smaller flasks for smoother sipping, especially early when GI tolerance is fickle.
Strength: maintain the creatine but be more consistent with two short strength sessions per week; durability helps late race.
Swim: I think I need to double down on this and build it into my program.
Bike: I can get more out of the bike as well. Trainnig volume can go up without compromising the load too much.
The big picture for busy athletes
Consistency: You don’t need monk-level mileage to run well. You need clarity and consistency. Pick one or two quality run sessions you never miss, pad the week with low-impact aerobic work on the bike, and spend your discipline on fuelling:
Carb-load properly (8–12 g/kg across 24–48 h, biasing low fat/protein).
Race-morning: low-fat, low-protein, high-carb breakfast you’ve practised.
On course: push to the highest carb rate you can comfortably tolerate (train the gut), and respect your personal sweat rate with pragmatic fluid stops.
Caffeine: dose it, don’t wing it.
Supplements: creatine and beta-alanine are keepers; bicarb when you’ve rehearsed it; pine bark extract is “watch this space,” not gospel.
Three years, three Sydney Marathons: 3:29 → 3:13 → 3:05. The course didn’t get easier; my choices got better. I’m qualified for Boston, still chasing sub-3, and absolutely getting that Katz’s pastrami sandwich—yes Jan, you’re buying the flight.
Cheers,
Scott