You step on the scale on a Monday morning. 82kg. Same as last month. Same as six months ago. You've been training ten hours a week, eating what you think is reasonably well, and the number won't move. So you cut more food. Ride longer. Skip breakfast before the Sunday group ride. Maybe try that intermittent fasting thing someone on Reddit was raving about.
And three months later you weigh 80kg, you've lost half a kilowatt off your FTP, your knees ache on every climb, and you're catching every cold that passes through the office. You're lighter. You're also slower.
Here's the thing nobody tells you about the number on the scale: it's almost useless for understanding whether you're actually getting faster on a bike. Two riders at 80kg can have completely different power-to-weight ratios, completely different climbing speeds, and completely different metabolic health. The number is the same. The bodies inside that number are not even close.
This is particularly true after 40, when the rules change in ways that catch even experienced cyclists off guard. Muscle loss accelerates. Hormonal shifts alter where fat sits and how readily it comes off. Recovery takes longer. The margin for error on nutrition gets thinner. And the approach that worked at 32 — ride hard, eat less, watch the weight drop — will actively cost you watts at 47.
Let me break this down properly. Body composition management is one of the trickiest areas of cycling nutrition for riders over 40, because the margin for error shrinks with every passing year.
Why the scale is a terrible performance metric
Your body weight on any given morning is a composite of at least five variables, and only one of them matters for cycling performance.
Muscle mass — the tissue that produces power. This is what you want more of. It's denser than fat, so gaining muscle can make the scale go up while your body composition improves and your watts-per-kilo actually gets better.
Fat mass — stored energy you're carrying up every hill. This is the component you want to reduce, within reason. But fat loss on its own, without preserving muscle, produces a lighter cyclist who is also a weaker one.
Water — fluctuates by 1-2kg daily based on hydration, sodium intake, heat, and how much you sweated on yesterday's ride. A single post-ride weigh-in can show a drop that means absolutely nothing about body composition. You've just lost fluid.
Glycogen — stored carbohydrate in your muscles and liver. Every gram of glycogen holds roughly 3g of water. A fully carb-loaded cyclist carries 1.5-2kg more than a depleted one. So when you "lose 2kg" after three days of low-carb eating, you've mostly emptied your glycogen stores. You haven't lost fat. You've lost fuel. And your next ride will confirm it.
Gut contents — food in transit. This varies by 0.5-1kg depending on when and what you last ate.
Add those up and your scale weight can swing 2-3kg within a single day without any change in actual body composition. The cyclist who weighs themselves every morning and reacts to each number is chasing noise.
When Asker Jeukendrup talks about body composition monitoring in athletes, he's explicit about this: the scale is a crude instrument that gives a crude answer. The useful question isn't "how much do I weigh?" It's "how much of what I weigh is producing power, and how much is just along for the ride?"
How to actually measure body composition
Not all measurement methods are equal, and the differences matter enough that choosing the wrong one can send you in entirely the wrong direction.
DEXA scanning — the gold standard
Dual-energy X-ray absorptiometry gives you a full breakdown of bone mineral content, lean tissue mass, and fat mass across your entire body. It's accurate to within 1-2% for body fat percentage, and critically, it shows you regional distribution — where the fat and muscle actually sit.
For a masters cyclist, that regional data is worth every penny. You can see whether you're carrying disproportionate visceral fat (a health marker that matters independently of total body fat), whether your leg lean mass is adequate for the power you're trying to produce, and whether one side has notably more muscle than the other.
The downside: DEXA scans cost $75-150 per session depending on where you live, and they're not available everywhere. You don't need them frequently. One scan to establish a baseline, then perhaps one every six to twelve months to track meaningful shifts. That's plenty.
Sam Impey, who's published extensively on body composition in athletes, recommends DEXA as the calibration tool — the one measurement that tells you where you actually stand, so you can interpret cheaper methods more accurately going forward.
Callipers — the practical middle ground
Skinfold calliper measurements, taken by a trained practitioner using a standardised protocol (typically the Jackson-Pollock 7-site or ISAK method), can track body composition changes reliably over time. The key phrase there is "trained practitioner." The same person, using the same technique, measuring the same sites, every eight to twelve weeks. That produces useful trend data.
Where callipers fall apart is when different people take the measurements, when the technique varies between sessions, or when you try to do it yourself in front of a bathroom mirror. Inter-tester variability with callipers is substantial — two different practitioners can measure the same person and get readings 3-4% apart. That's not a measurement error you can work with.
Find one good practitioner. Stick with them. The absolute number matters less than the direction of change over time.
Bioelectrical impedance — the bathroom scale lie
Those bathroom scales that claim to measure body fat by sending an electrical current through your feet? They're essentially useless for tracking meaningful changes in body composition.
Let me be really clear about this. BIA scales are affected by hydration status, time of day, whether you've just trained, how much you've eaten, and even the temperature of your skin. Tim Podlogar has pointed out that a BIA reading can shift 3-5% within the same day based on nothing more than whether you've had a glass of water. The signal-to-noise ratio is terrible.
They have one narrow use case: if you weigh yourself under identical conditions every week (first thing in the morning, fasted, same day, no training the day before) and you average the readings over a rolling four-week window, you can sometimes spot a trend over months. But that's an enormous amount of effort for a tool that still can't tell you accurately whether you've lost fat, muscle, or water.
If you own one, stop treating the body fat number as meaningful. Use it as a scale. Weigh yourself. Ignore the percentage.
Realistic targets for the over-40 cyclist
This is where the cycling internet gets particularly dangerous, because the targets most riders have in their heads come from World Tour professionals — athletes who have full medical teams, daily blood work, and nutritional support structures that don't exist for the rest of us.
For male masters cyclists, a realistic and healthy body fat range is 12-18%. The lower end of that range — 12-14% — is where you'll be properly lean, where climbing performance is strong, and where health markers are still solid. Going below 12% starts to produce diminishing returns: the marginal watts-per-kilo gain from losing another kilogram of fat gets smaller, while the health costs — hormonal suppression, immune compromise, poor sleep, reduced bone density — get larger.
For female masters cyclists, the equivalent range is 18-25%. Women carry essential fat in different patterns and at higher percentages than men, and the consequences of going too low are more acute and arrive sooner. Dr Sharon Madigan at Sport Ireland Institute is unambiguous on this: female cyclists attempting to reach body fat levels below 18% without professional supervision are taking a genuine health risk, with menstrual disruption often the first and most visible symptom of a deeper systemic problem.
Here's what those ranges actually look like in practice:
| Category | Male (Body Fat %) | Female (Body Fat %) | |---|---|---| | General fitness cyclist | 18-22% | 25-30% | | Competitive masters cyclist | 12-18% | 18-25% | | Very competitive / regional | 10-14% | 16-20% | | Below this: health risks escalate | <10% | <16% |
Those pro cyclists you see at the Tour at 6-7% body fat? They hold that for perhaps three to four weeks around their peak race, not year-round. And even then, the growing evidence from World Tour team doctors suggests that some of those riders are paying a long-term health price for those numbers. The model is changing at the professional level precisely because the costs have become clearer.
You're not being paid to race. You're training to be fast, healthy, and riding well at 50, 55, 60. The target should reflect that. The race weight guide covers how to find a sustainable target based on performance data, not aspiration.
The seasonal approach to body composition
Year-round restriction doesn't work. It didn't work for the pros — that's why the sport moved away from it — and it doesn't work for you. The model that does work is seasonal: specific windows for composition change, separated by longer windows where you eat to support the training and let the body do its thing.
Off-season (October-November): the composition window
This is when the work gets done. Training load is naturally lower during the transition and early base phases, which means a modest caloric deficit doesn't compete with performance adaptation. Your body isn't trying to recover from intervals or absorb big training stimuli, so it can tolerate a small energy restriction without the cascade of problems you'd get mid-season.
The target: a deficit of 200-400 calories per day, primarily on rest days and easy riding days. Full fuelling on any day where you're doing structured work. Rate of loss: 0.3-0.5kg per week. Not faster. A 48-year-old body that's running a 1,000-calorie deficit will cannibalise muscle, suppress hormones, and produce exactly the kind of metabolically damaged outcome you're trying to avoid.
Over an 8-10 week composition window, that's 2.5-5kg of fat loss. For most masters cyclists carrying 5-10kg above their performance weight, one or two annual composition phases gets them where they need to be across two to three years.
Base phase (December-February): maintenance
No deficit. Match energy intake to training output. The aerobic base you're building during this phase requires adequate fuelling to produce the mitochondrial adaptations you're after. Running a deficit through base training is like building a house while rationing the concrete. The structure ends up weaker.
This is the phase where many riders go wrong because they're impatient. They see the composition phase working and want to keep going. Don't. The adaptation you're earning from base training has a higher performance return than the additional gram of fat loss. Trust the process.
Build and race phases (March-June): full fuelling
Body composition should be stable or very slowly shifting here — and any shift should come naturally from the increased training load, not from deliberate restriction. Dr David Dunne at INEOS made this point clearly when he was on the podcast: you arrive at race lean from the work you did months earlier, not from dieting into your target event.
Attempting a significant caloric deficit during a build or race phase produces stalled training, compromised recovery, suppressed immunity, and — paradoxically — weight that won't come off because the body is protecting itself against a perceived survival threat. You end up flat, tired, and the same weight.
Post-season (July-September): intentional regain
This is the bit nobody wants to hear. Allowing a small weight regain of 1-2kg during the post-season is not failure. It's physiology. Your body needs periods of caloric abundance to reset metabolic rate, restore hormonal function, and consolidate the training adaptations from the season. The cyclist who stays lean year-round often has lower testosterone, worse sleep, and a metabolic rate that has downregulated to match the chronic restriction.
Think of it as periodisation applied to nutrition, not just training. Hard phases and recovery phases. Structure produces better outcomes than relentless restriction.
RED-S: the cost nobody talks about
Relative Energy Deficiency in Sport is the formal name for what happens when an athlete chronically underfuels relative to their training load. And it's far more common in amateur cyclists than most people realise.
Here's how it typically presents in a masters cyclist. You're training consistently — eight to twelve hours a week. You're eating what looks like a normal amount of food. Your weight might even be stable. But your energy availability — the energy left over after exercise for your body to run its essential systems — is chronically low. Below 30 kcal per kilogram of fat-free mass per day, your body starts rationing.
What gets rationed first? The systems your body considers non-essential for immediate survival. Reproductive hormones. Bone remodelling. Full immune function. Thyroid output. These are the exact systems that determine your long-term health and your ability to recover from and adapt to training.
The symptoms are insidious because they build slowly. Persistent fatigue that doesn't resolve with a rest week. Getting sick more often — three or four colds a season instead of one. Sleep disturbance. Declining performance despite doing all the right training. Loss of libido that you attribute to stress or age. Mood going flat.
And here's the part that catches people off guard: chronic underfuelling often makes it harder to lose body fat, not easier. The thyroid downregulation reduces your basal metabolic rate. Non-exercise activity thermogenesis drops — you move less throughout the day without realising it. The body clings to fat stores because it interprets the situation as a survival challenge. You eat less, you train hard, and the weight holds.
The 2023 IOC consensus statement led by Margo Mountjoy is unequivocal: RED-S affects all athletes, male and female. In male cyclists, it's dramatically underdiagnosed because the symptoms — fatigue, stalled performance, declining sex drive — get attributed to normal ageing. "I'm 46, this is just what happens." Often, it's not.
If any of this sounds familiar, the energy availability calculator gives you a working estimate. Below 30 kcal/kg FFM/day is a red flag that warrants a conversation with a sports dietitian, not another reduction in calories.
When weight loss actively costs you watts
There's a specific set of warning signs that tells you your energy restriction has crossed from productive into destructive. Learn them. Respect them.
FTP starts dropping. Not the normal fluctuations from fatigue and freshness, but a consistent downward trend across four to six weeks. If you're in a body composition phase and your FTP drops by more than 3-5%, the deficit is too large or you're not protecting your training sessions with adequate fuelling.
Resting heart rate climbs. A reliable morning resting heart rate that starts trending 3-5 beats above your baseline, measured consistently on waking, is an early signal of accumulated stress. The deficit is one stressor. The training is another. The body can handle one at a time. Both together, in a masters athlete with less recovery capacity, produces overload.
Sleep deteriorates. Waking at 3am and unable to get back to sleep is a classic sign of cortisol dysregulation driven by chronic energy deficit. Your body is stressed, and the hormonal response is to spike cortisol at a time when it should be at its lowest. If this starts happening during a composition phase, you're underfuelling.
You're getting injured more. Muscle strains, niggles that won't resolve, or bone stress reactions are all associated with low energy availability. Cycling is non-weight-bearing, which already puts bone density at a disadvantage compared to running. Add chronic underfuelling and the risk compounds.
Training motivation collapses. Not the normal "I don't fancy it today" that every cyclist feels occasionally, but a persistent inability to care about sessions, race goals, or the sport itself. This is one of the later-stage psychological effects of RED-S and it signals that the deficit has been too large for too long.
The moment any of these appear, the correct response is to increase calories — particularly carbohydrate around training — not to push through. More discipline in the face of these symptoms produces more damage, not more results. The performance cost of continuing an aggressive deficit is always larger than the performance benefit of the marginal weight loss.
Protein and the anabolic resistance problem after 40
Here's where age changes the equation. After 40, your body becomes progressively less efficient at converting dietary protein into muscle tissue. The research calls this anabolic resistance, and it's one of the primary reasons masters athletes lose muscle mass — not because they don't train, but because the same protein dose that maintained muscle at 30 is no longer sufficient at 48.
The mechanism is well-documented. Muscle protein synthesis — the process of building and repairing muscle tissue — requires a threshold dose of the amino acid leucine to switch on fully. In a younger athlete, that threshold is around 2-2.5g of leucine, which you get from roughly 20-25g of protein. In a masters athlete, the threshold climbs to 3-4g of leucine, requiring 35-40g of high-quality protein to achieve the same synthetic response.
What this means in practice: the 20g protein shake that was adequate at 32 is no longer hitting the threshold at 47. The muscle isn't being maintained. Over months and years, the accumulated deficit shows up as sarcopenia — loss of muscle mass that directly reduces power output and metabolic rate.
The research from Stuart Phillips's lab at McMaster University has established that masters athletes need 1.6-2.2g of protein per kilogram of body weight per day to maintain lean mass, with the higher end of that range appropriate during any period of energy restriction. For an 80kg cyclist, that's 128-176g of protein daily.
Distribution matters as much as total intake. Four to five protein-rich meals, each containing 35-40g, produces a better muscle protein synthesis response than two or three larger meals. The overnight fasting period is particularly costly for masters athletes — the 8-10 hours without protein intake represents a long window of net muscle breakdown. A casein-rich evening meal or pre-bed protein dose of 30-40g can partially offset this, which is why the data on pre-sleep protein for cyclists keeps coming back positive.
During a composition phase, protein becomes even more critical. The caloric deficit creates a catabolic environment — your body is looking for energy, and muscle tissue is a potential source. Without adequate protein and a strength training stimulus to signal that the muscle is needed, some of the weight you lose will be lean tissue. You'll weigh less, but a proportion of the lost weight was engine, not cargo. Watts-per-kilo goes sideways or down.
The practical minimum during a composition phase for a masters cyclist: 2g per kilogram of body weight, spread across the day, with particular attention to post-training and pre-sleep doses. This is non-negotiable if you want to lose fat and keep power.
A practical framework for body composition management
Enough theory. Here's how this looks as a working system across a calendar year.
Step 1: Establish your baseline
Get a DEXA scan. One scan. It costs the same as two or three tubs of cycling-specific supplements and gives you data you can actually act on instead of marketing promises. Know your actual body fat percentage, your lean mass, and your regional distribution. This number is your starting point, not a guess from a bathroom scale.
If DEXA isn't accessible, find a physiotherapist or sports scientist who does skinfold measurements using a standardised protocol. Get measured. Write the numbers down.
Step 2: Set a realistic target
Use the ranges above. If you're a 48-year-old male at 22% body fat, your initial target is 16-18%, not 10%. That's achievable across two composition phases. If you're at 16%, your target might be 13-14%, which is one phase of careful work. The target should feel conservative. You can always reassess after hitting it.
Step 3: Time the composition phase
Place it in the off-season or early base — October through December for a Northern Hemisphere rider targeting summer events. Training load is lower. The deficit won't compete with performance adaptation. Eight to ten weeks is the window. Not longer.
Step 4: Create a modest deficit on rest days
200-400 calories below maintenance on rest and easy days. Full fuelling on any training day with structured work. The deficit comes from slightly smaller rest-day portions, not from removing food around training. Carbohydrate is the variable — protein and fat stay consistent.
Step 5: Protect protein
1.6-2.2g per kilogram daily. Four to five doses of 35-40g. Post-ride recovery shake or meal. Pre-bed casein or cottage cheese. Don't let a single meal go below 30g.
Step 6: Strength train twice a week
Two sessions, 30-45 minutes each. Compound movements that load through a full range — leg press, lunges, Bulgarian split squats, step-ups, hip thrusts. Upper body push-pull work: press-ups, dumbbell rows, overhead press. Core stability. The goal is to send a clear signal to the body that muscle tissue is in use and should be preserved. Without this signal during a deficit, muscle loss is inevitable.
Step 7: Monitor the right things
Track body composition every eight to twelve weeks using callipers or DEXA, not the scale every morning. Track your FTP. Track your morning resting heart rate. Track sleep quality. Track illness frequency. If FTP drops, resting heart rate climbs, sleep fragments, or you're catching every bug going — the deficit is too aggressive. Pull back immediately.
Step 8: Stop when the window closes
After eight to ten weeks, end the composition phase regardless of whether you've hit your target. Return to maintenance calories. Let the body stabilise. Assess progress. If you need more composition work, schedule another phase in four to six months. Patience compounds. Impatience damages.
The psychological dimension
Body composition in cycling is wrapped up in identity, comparison, and a culture that has historically rewarded thinness over health. The rise of power meters has helped — watts don't lie, and a rider producing 280 watts at 82kg with 16% body fat is categorically faster than the same rider producing 250 watts at 76kg with 12% body fat, even though the lighter rider "looks" faster.
But the comparison instinct runs deep. You see someone lighter on the group ride pulling away on a climb and the reflex is "I need to lose weight." Not "I need more watts." Not "I need to pace that climb differently." Not "that rider has been training for twenty years and has genetics I don't share." The reflex goes straight to weight.
Catch that reflex. Question it. Run the numbers on your race weight calculator instead. Ask whether the watts you'd lose getting to that weight outweigh the watts-per-kilo you'd gain. Often, especially in masters cyclists, the answer is no. The weight loss costs more than it saves.
Your body at 47 is not the body you had at 30, and treating it as though it should look or weigh what it did at 30 is a reliable path to chronic underfuelling, performance decline, and unhappiness on the bike. Performance body composition for a masters cyclist is the weight at which you produce the most watts, recover properly, sleep well, don't get sick, and can sustain for months without restriction. That number is usually higher than you think.
What to do next
Start with one DEXA scan. Know where you actually stand, not where your bathroom scale tells you. Use the body composition calculator for a working estimate if you need a number right now, and the energy availability calculator to check whether your current intake is matching your training load. The race weight calculator gives you a realistic target based on performance ranges rather than aspiration.
If this rang a few bells — the stalled weight, the creeping fatigue, the niggling question of whether you're eating enough or too much — the conversation is worth having with people who get it. The Not Done Yet community runs regular body composition Q&As, and it's the one topic where the discussion goes deep because it's the topic most cyclists care about privately and talk about least publicly. You're not the only one trying to work this out. You're just the only one who thinks they are.