The Complete Guide to Sports Nutrition for Endurance Athletes
Most endurance athletes get their training plan sorted long before they get their fuelling sorted. You'll find riders with a meticulously periodised twelve-week block who still bonk at kilometre 130 of a sportive, or runners who nail every threshold session but blow up in the last 10k of a marathon because they treated race-day nutrition as an afterthought. Fuelling isn't a footnote to training — it's the thing that determines whether your training actually shows up on the day.
This is a practical, numbers-led sports nutrition guide for endurance athletes covering the four things that matter most: carbohydrate intake, hydration and electrolytes, gut training, and recovery. None of it is complicated once you understand the underlying logic, and none of it requires an expensive lab test to get 90% of the benefit. Treat this as the reference you come back to before a big block or a goal race.
Getting Your Carbohydrate Intake Right
The single biggest lever in endurance nutrition is carbohydrate intake per hour, and the guidance has shifted considerably over the last decade. Where 30-60g of carbs per hour was once the standard advice, current sports science supports much higher intakes for anything over 90 minutes: 60-90g per hour for most athletes, and up to 90-120g per hour for well-trained endurance athletes who have built up to it gradually.
The reason you can't simply eat 90g of glucose alone is absorption. A single carbohydrate source (glucose or maltodextrin on its own) tops out at an absorption rate of roughly 60g per hour, because it all uses the same intestinal transporter (SGLT1). Add fructose, which uses a separate transporter (GLUT5), and you can push total absorption significantly higher — this is why a glucose-to-fructose ratio of around 1:0.8 (commonly simplified to "1:1") is the standard formula behind most modern gels, chews and drink mixes. It isn't marketing — it's genuinely how you get more fuel from your gut into your bloodstream without it sitting there causing problems.
Hydration and Electrolytes: The Numbers That Matter
Sweat rate varies hugely between individuals — anywhere from 0.5 to over 2 litres per hour — so generic "drink X ml per hour" advice is only ever a starting point. A more useful approach is to weigh yourself before and after a typical hard session (same conditions, minimal drinking) and work out your rough hourly loss. Aim to replace roughly 80% of what you lose during exercise; replacing 100% on the move is rarely necessary and can tip you toward the opposite problem.
Sodium is the electrolyte that matters most for endurance sport. Sweat sodium concentration ranges from around 200mg to over 1,500mg per litre depending on the individual, with most athletes losing somewhere in the 500-700mg per litre range. If you finish long sessions with visible white salt marks on your kit, you're likely a heavier-than-average "salty sweater" and should be proactively topping up sodium during efforts over 90 minutes, not just relying on what's in your carb source. Under-replacing sodium on very long, hot days is a genuine risk factor for hyponatraemia, which is far more dangerous than mild dehydration. A simple field test: if you're cramping repeatedly in the same session despite adequate carbohydrate and fluid, sodium is the first thing to increase before you look anywhere else, particularly in heat or humidity where losses climb sharply.
Temperature changes the maths considerably. For every 5°C above around 20°C, expect your sweat rate and sodium losses to increase noticeably, which means your hydration and electrolyte strategy for a summer sportive or an autumn race in cooler conditions genuinely needs to be different plans, not the same plan executed at different speeds.
Training Your Gut Like You Train Your Legs
Gut tolerance to carbohydrate is trainable, and this is probably the most underused piece of sports nutrition for endurance athletes. If you've only ever taken 30-40g of carbs per hour in training, jumping to 90g on race day is asking for trouble — nausea, bloating and GI distress are the predictable result of an untrained gut suddenly being asked to process far more than it's used to.
The fix is straightforward: practise your race-day fuelling strategy in training, at race intensity, on a regular basis — ideally weekly during your build phase. Start at your current comfortable intake and increase by roughly 5-10g per hour every couple of weeks. Most athletes can comfortably reach 90g per hour within six to eight weeks of consistent practice. This is exactly the same adaptation principle as training your muscles or your cardiovascular system — the gut responds to a progressive, specific stimulus.
Building a Sports Nutrition Plan for Endurance Athletes That Actually Survives Race Day
A good sports nutrition endurance athletes guide isn't a single number — it's a plan that accounts for effort duration, weather, course profile and your own individual tolerance. As a rough framework: sessions under 60 minutes rarely need fuelling beyond a normal pre-session meal; 60-90 minutes benefits from 30-60g of carbs per hour; anything beyond 90 minutes should be working toward 60-90g per hour, built up gradually as described above.
Recovery nutrition deserves equal billing. The old idea of a rigid "30-minute window" has softened in the research, but getting 1-1.2g of carbohydrate per kilogram of bodyweight and 20-40g of protein into you within a couple of hours of a hard session still meaningfully speeds glycogen resynthesis and reduces the muscle soreness that compounds across a heavy training week. Tart cherry is worth knowing about here specifically: Montmorency tart cherries are rich in anthocyanins, compounds shown in several trials to reduce exercise-induced oxidative stress and markers of inflammation, which is one reason they've become a fixture in serious endurance athletes' recovery routines alongside the basics of carbs, protein and sleep.
What We Use at FTP Endurance Fuel
We built our own fuelling around the principles above rather than the other way round. Our Mixed Fruit Energy Pastilles use a glucose-fructose blend designed to work with your gut's absorption pathways rather than against them, making them easy to eat consistently during long rides or runs without the gut distress that catches so many athletes out mid-race. For a change of flavour, our Tart Cherry Energy Pastilles deliver the same usable carbohydrate in a tart cherry flavoured chew. If you want real Montmorency tart cherry, it's in our Power Fluids drink mix (3g per serving).
None of this needs to be complicated, but it does need to be deliberate. Work out your rough sweat and sodium losses, build your carbohydrate tolerance progressively in training rather than guessing on race day, and give recovery the same attention you give the session itself. Get those three things right and consistently, and your nutrition will stop being the reason your training doesn't show up — start practising your fuelling strategy on your next long session and take the guesswork out of race day.
