If you are training hard, eating carefully, and still not losing weight, the advice you are following was probably written for someone who does not train. Dr Sharon Madigan, Head of Performance Nutrition at the Sport Ireland Institute and a nutritionist to Olympic athletes for the best part of three decades, makes the case that the classic calories-in-versus-calories-out model breaks down the moment you add 12 hard hours a week. She walked through the whole argument on Struggling to Lose Weight? This is Why! on the Roadman Cycling Podcast, and most of what she says runs against the grain of standard diet advice.
Key Takeaways
• Losing weight while training hard means periodising your nutrition, not flat-restricting calories every day • Underfuelling today's session creates tomorrow's binge — fuel for the work you are about to do, not what you did yesterday • Think in 24- to 48-hour blocks: Saturday's dinner is part of Sunday morning's fuel • Chronic underfuelling drops immunity because white blood cells run primarily on carbohydrate • Easy days still need fuel — roughly 5–7g of carbohydrate per kg even when the riding is gentle • Most cyclist gut issues come from mismatched fuelling, not food intolerance • The deficit belongs in the low-demand windows, never wrapped around your key sessions
Why Calories In Versus Calories Out Fails Endurance Athletes
Most weight-loss advice is built on data from sedentary populations who are not trying to hold training intensity while running a deficit. Put a 12-to-15-hour training week on top of "move more, eat less" and the maths quietly turns against you.
Madigan's framing is that the target is a moving one. "If someone's decided they're going to do a lot more on the bike compared to six months ago, that's a big change. You've got to readapt and readjust to suit that particular outcome." The trap is anchoring to what worked before. You might have dropped weight last winter on 2,000 calories and five hours a week. Now you are doing twelve hours at higher intensity and still holding that same 2,000-calorie line — and the deficit has gone from sensible to punishing.
What follows is predictable. Immunity slips first, because white blood cells lean on carbohydrate as fuel, so you start catching every bug going round. Training quality drops because you are permanently underfuelled. Then willpower gives way and you binge, usually on exactly the foods you have been white-knuckling all week. That is the yo-yo so many club riders know intimately: strict all week, underfuelling the key sessions, then face-deep in a tub of ice cream on Saturday night wondering where it went wrong.
The deficit itself is not the enemy. The timing is. A deficit that sits on top of your hardest sessions costs you the adaptation you are training for. A deficit parked in the quiet windows barely registers.
The 24-Hour Fuelling Method
Madigan's central move is to stop thinking in days and start thinking in training blocks. "There's no magic switch at 12 midnight," she says. "Let's get out of this way of thinking about a day. Let's think about the period of time and really fuel for that 24-hour period that might have two sessions in it."
In practice, your fuelling for a Sunday 9am long ride starts on Saturday evening. Saturday's dinner is not just Saturday's meal — it is the opening of Sunday's tank. You add carbohydrate at lunch, take an afternoon snack you would normally skip, make dinner a little bigger, maybe add something before bed. The energy does not reset at midnight, and your eating should not pretend it does.
For matching fuel to intensity, her rough framework runs by bodyweight across the 24 hours surrounding the session:
- Easy riding: 5–7g of carbohydrate per kg
- Moderate intensity: 7–10g per kg
- Hard sessions and racing: 8–12g per kg, plus around 1g per kg per hour on longer efforts
Work it through for a 70kg rider with a hard three-hour ride: roughly 700g of carbohydrate across the 24-hour window, with about 200g of that taken on the bike. The numbers look large precisely because the day before, the ride itself, and the recovery after are one continuous fuelling job rather than three separate meals on a calendar.
This is also where the deficit lives without doing damage. You hold the carbohydrate around the work that matters and trim it from the meals furthest from training. The weekend long ride gets fed properly; the quiet Tuesday afternoon is where you eat a little less.
Why Your Gut Problems Are a Fuelling Problem
Madigan sees gut trouble in a large share of the cyclists she works with, and she is blunt that the usual suspect — food intolerance — is rarely the culprit. The more common cause is mismatched fuelling.
The sequence is familiar. You underfuel through the week to lose weight. You roll out for the Saturday group ride already in a deficit, so your gut is working on empty before you have turned a pedal. Then you try to claw it back mid-ride with a stack of gels and sports drink. "If you're under-fuelling, you're not putting in enough fuel for the gut to do the job that they're there to do. Then suddenly you might be putting in high volumes of gels or foods that contain a big isotopic load of carbohydrate coming in at one time — it's very hard to work on that."
The gut cannot cope with a sudden flood after running dry, so you cramp and bloat. Next time you pull fuelling back because you remember how rough you felt — and the cycle tightens. The fix is not an expensive intolerance test, which Madigan rates poorly on evidence. It is better timing and better choices:
- Split the load. Spread pre-ride fuel between the night before and the morning of, rather than cramming it all into the two hours before you ride.
- Lower the residue. With a sensitive gut, plain cereals like cornflakes or rice-based options sit easier than high-fibre oats before a ride.
- Use liquids. A smoothie with yoghurt, milk, oats and fruit can deliver 600–800 calories and 60–80g of carbohydrate without the volume that triggers problems.
What This Means for Your Training
Stop trying to lose weight and train flat-out at the same time, every day. Pick your battles off your training calendar instead.
During heavy blocks, the job is to fuel the work. Weight tends to come off on its own when you are doing twelve to fifteen quality hours a week, provided you are not chronically underfuelled and triggering binges. Save the deliberate deficit for lower-volume phases and base work — and even then, protect your key sessions. If Tuesday is your hard interval day, you eat properly Monday night and Tuesday morning regardless of what the scale is doing.
Use Madigan's three-zone guide to stop treating easy days as nutritional rest days. A two-hour endurance ride does not need threshold-day fuelling, but it still needs fuel; ride it on fumes all week and you are flat by Thursday. And treat your gut as trainable — most digestive trouble is a timing and energy problem, not a list of foods to cut. Practise your fuelling in training, split your intake, and build tolerance gradually.
If you are fuelling well and the weight still will not shift — or the training is stalling alongside it — the limiter may not be on your plate at all. The Plateau Diagnostic looks at your training, recovery and fuelling together and shows you where the real constraint sits. Three minutes. Free.