Here's what nobody tells you about cycling nutrition. The thing that's probably costing you the most watts has nothing to do with your training plan, your bike, or your FTP. It's what you're eating. Or more accurately, what you're not eating, when you're eating it, and the small little leaks that add up to real performance losses over weeks and months.
We see these mistakes constantly. They come through on the podcast emails, in the Skool community, on every ride where someone bonks and can't figure out why. The same patterns, the same errors, the same confused looks when the power numbers don't match the training effort.
The good news is every single one of these is fixable. Not with a complete diet overhaul. Not with supplements or expensive products. With specific, practical changes you can make this week.
Mistake 1: Chronic Under-Fueling
This is the big one. The one that underpins almost everything else on this list.
Most cyclists think they eat too much. The reality, based on the research and what we see in the community, is that most serious amateur cyclists chronically under-eat. Not by a lot. By maybe 300-500 calories a day. But compounded over weeks and months, that deficit creates a cascade of problems that go far beyond feeling a bit tired on a Tuesday night ride.
The 2018 IOC consensus statement led by Margo Mountjoy identified this pattern formally as Relative Energy Deficiency in Sport — RED-S. It replaced the old "female athlete triad" concept because they realised it wasn't just a female problem. Male endurance athletes are hit just as hard.
Here's what happens when you chronically under-fuel. Your testosterone drops. Your thyroid function slows. Your cortisol rises. Your bone density decreases. Your immunity tanks — you catch every cold going around the club. Your sleep quality deteriorates. And your power output drops, sometimes by 5-10%, without any obvious explanation on the training side.
Professor Louise Burke at the Australian Institute of Sport has been publishing on this for over a decade. The mechanism is basic — your body doesn't know you're trying to "eat clean" or "lean up." It registers a sustained energy deficit and starts shutting down non-essential systems to protect itself. Reproduction, bone remodelling, and immune function get cut first. Then performance follows.
The fix: Calculate your resting metabolic rate and add your training expenditure. For most male cyclists training 8-12 hours a week, that's somewhere between 2,800 and 3,500 calories a day. Not 2,000. Not 1,800. If you've been eating significantly under those numbers for months, you've been leaving watts on the table. Increase intake gradually — 200 calories per day for two weeks — and watch what happens to your energy, sleep, and power.
Mistake 2: Poorly Executed Fasted Rides
Let me be really clear about this. I'm not saying fasted training has no value. There's solid research — particularly from Louise Burke and her periodised nutrition work — showing that training with low carbohydrate availability can enhance fat oxidation and mitochondrial biogenesis. The science is real.
But that's not what most cyclists are doing when they skip breakfast and head out for three hours on a Saturday morning.
What most people call "fasted riding" is actually just under-fueling with extra suffering. You end up bonking 60km from home and hating your life. That's not metabolic training. That's a survival situation.
Burke's research is specific about the protocols that work. Short rides. Low intensity. Zone 2 only. Under 90 minutes. And critically — not on days when you have hard intervals scheduled. The whole concept of "train low, compete high" from her work with the Australian track cycling team means you deliberately restrict carbohydrate availability on easy days to drive adaptations, then fuel fully for quality sessions.
The problem is the cycling internet turned this nuanced, periodised approach into "skip breakfast and ride hard." That's how you end up with suppressed immunity, poor recovery, and the exact chronic under-fueling from mistake number one.
The fix: If you want to use fasted training, limit it to Zone 2 rides under 90 minutes. Never do intervals fasted. Never do group rides fasted. And never do it more than two or three times per week. On every other ride, eat breakfast 2-3 hours beforehand — 1-2g of carbohydrate per kilogram of bodyweight. Porridge with banana and honey. Toast with peanut butter. Nothing complicated.
Mistake 3: Fiber Timing
This one is sneaky because the food itself isn't the problem. Fiber is essential. Whole grains, vegetables, legumes — all of it is brilliant for your long-term health, your gut microbiome, and your overall nutrition quality.
The issue is when you eat it relative to hard training or racing.
During exercise, blood flow is diverted from your digestive system to your working muscles. That's basic physiology. When you've got a belly full of high-fiber food — oats with seeds, a big salad, lentil soup — your gut is trying to process indigestible material with significantly reduced blood supply. The result is cramping, bloating, urgency, and the kind of GI distress that ends races.
Research from Asker Jeukendrup's lab at Loughborough (and later at the Gatorade Sports Science Institute) consistently showed that pre-exercise meals high in fiber, fat, and protein are the primary predictors of GI symptoms during endurance events. Not the in-ride nutrition. Not the gels. The food you ate three hours before the start.
A 2014 study by de Oliveira and Burini in the Journal of the International Society of Sports Nutrition found that athletes who reduced fiber intake in the 24 hours before competition had significantly fewer GI complaints than those who maintained their normal high-fiber diet.
The fix: On the evening before a hard training session or race, and on the morning of, switch to low-fiber, low-residue foods. White rice instead of brown. White bread instead of wholemeal. Banana instead of an apple with skin. Smooth peanut butter instead of the crunchy whole-nut version. Save your high-fiber meals for recovery days and easy training days. You're not reducing fiber overall — you're timing it away from performance.
Mistake 4: Not Fueling During Training Rides
"I only fuel for races." I hear this constantly. And it's one of the most counterproductive things you can do as a cyclist.
Here's the logic most people use: training rides are for burning calories and building fitness, so eating during them is counterproductive. This makes intuitive sense and is completely wrong.
When you don't fuel during training rides over 90 minutes, two things happen. First, the quality of your session drops. Your power output in the second half of a long ride or during late-in-ride intervals is measurably lower when glycogen is depleted. You're training, but you're training a depleted, underperforming version of yourself. Second, you never train your gut to process fuel at intensity — which means on race day, when you suddenly ask your digestive system to handle 80-90g of carbohydrate per hour, it revolts.
Asker Jeukendrup has been banging this drum for years. The gut is trainable. The transporters that absorb glucose and fructose upregulate with repeated exposure. But that adaptation requires consistent practice — taking in carbohydrate during training, at the rates you'll use in racing, week after week.
Professor Stephen Seiler, when I had him on the podcast, made the point that training quality drives adaptation. Not training volume. Not training suffering. Quality. And quality requires fuel.
The fix: For any ride over 90 minutes, take in 40-60g of carbohydrate per hour. For hard interval sessions, even if they're only 75 minutes, start fueling from the warm-up. Match your training fueling to your race fueling — same products, same timing, same quantities. This is how you build a gut that performs on race day instead of one that lets you down.
Mistake 5: The "I'll Eat When I Get Home" Mistake
You finish a two-hour threshold session. You stretch. You upload to Strava. You have a shower. You make coffee. You check your phone. Maybe you start preparing food. By the time you actually eat, it's been 90 minutes since you got off the bike.
That window matters far more than most cyclists realise.
The research on post-exercise glycogen resynthesis is clear and has been for decades. Ivy et al. published the foundational work back in 1988 — muscle glycogen resynthesis rates are 50% higher in the first 30 minutes post-exercise compared to two hours later. The enzyme glycogen synthase is most active immediately after exercise. Miss that window and you're starting your next session with partially depleted glycogen stores.
But it's not just about glycogen. Dr. Kevin Tipton's work on muscle protein synthesis showed that the post-exercise period is when damaged muscle fibers are most responsive to amino acids. Delaying protein intake by even two hours significantly reduces the muscle repair response. For cyclists trying to maintain or build lean mass — which is almost everyone over 40 — this matters enormously.
The fix: Have something ready before you ride. It doesn't need to be a gourmet meal. A protein shake with a banana. Greek yoghurt with honey and berries. A rice bowl you prepared the night before. The target is 1.0-1.2g of carbohydrate per kilogram of bodyweight and 25-40g of protein within 30 minutes of finishing. Prepare it before you ride so there's zero friction when you walk through the door.
Mistake 6: Drinking Too Much Plain Water
This one can actually be dangerous, and it's more common than people think.
Most cyclists know dehydration is bad. So they drink. A lot. Water bottles, hydration packs, stopping at every fountain. But plain water without electrolytes, consumed in large volumes during long rides, dilutes the sodium concentration in your blood. This is called hyponatremia, and it's been responsible for hospitalisations and even deaths in endurance events.
A landmark 2005 study by Almond et al. in the New England Journal of Medicine examined runners in the Boston Marathon and found that 13% had hyponatremia at the finish line. The primary risk factor wasn't the distance or the heat. It was drinking too much water relative to sodium losses.
Timothy Noakes — the South African sports scientist and author of Waterlogged — has argued extensively that the "drink before you're thirsty" advice propagated by the sports drink industry has caused more problems than it's solved. His position, supported by considerable evidence, is that drinking to thirst is a safer baseline than drinking to a predetermined schedule, especially when using plain water.
The point isn't to drink less. It's to drink smarter.
The fix: Add 500-1000mg of sodium per litre to your training and racing drinks. That's roughly one electrolyte tab or a quarter teaspoon of salt per 750ml bottle. On hot days or for rides over three hours, increase the sodium concentration. Stop using plain water for long rides entirely. And don't force-drink beyond thirst — if you're finishing rides with a sloshing stomach, you're over-drinking.
Mistake 7: Trying New Nutrition on Race Day
This is the one most people know about and still ignore.
Race morning. You're nervous. Someone in the car park offers you a gel you've never tried. The feed station has a drink you've never tasted. The cafe at the start has pastries that smell incredible. You think, "sure, what's the worst that can happen?"
The worst that can happen is your gut shuts down at kilometre 80 and you spend the last 40km alternating between cramping and searching for a hedge.
Jeukendrup's research at Birmingham showed that the gut adapts to specific carbohydrate types and concentrations over 5-10 repeated exposures. Each exposure upregulates the intestinal transporters — SGLT1 for glucose, GLUT5 for fructose — that allow absorption without osmotic distress. A new product introduces a new formulation, a new concentration, maybe a new sugar ratio. Your gut hasn't adapted to it. Under race-day stress, with reduced blood flow to the gut, that untested variable becomes the thing that ends your race.
This applies to everything. Gels, drinks, bars, real food, caffeine products, even the pre-race breakfast. If you haven't tested it in training at race intensity, it's a gamble.
The fix: Build your race nutrition plan at least 8 weeks before your target event. Use the exact products you'll race with on every hard training ride during that block. Test them at intensity, not just on easy rides. Know how many gels per hour you can handle, which drink concentration your gut tolerates, and what your pre-race meal looks like down to the specific foods and timing. Race day is execution, not experimentation.
Where It Gets Interesting
Here's what I love about this list. None of these mistakes require expensive equipment, a coaching qualification, or a complete lifestyle change. They're specific. They're fixable. And the compound effect of fixing even three or four of them is measurable in watts, recovery quality, and how you feel on the bike.
The science has finally caught up to what the best coaches and sports nutritionists have been saying for years. Fuel the work. Time your nutrients. Practise your race nutrition like you practise your race pacing. Small little leaks that add up to big performance losses — and every single one of them can be plugged this week.
If you want to go deeper on any of this — the specific protocols, the periodisation, how to structure your nutrition around your training calendar — that's exactly what we cover in the Roadman Cycling community. Real questions from real cyclists, answered with the same evidence-based approach you've just read.