Avitu | Blog
What Should You Eat Before a Key Workout? More Carbs, Less of Everything Else
Most riders plan a key session down to the watt. Four intervals of eight minutes at 105% of FTP, three minutes easy between. Then they eat the same breakfast they’d eat on a rest day: a big bowl of muesli, two eggs, some avocado toast. Session on point, nutrition needs some work.
That breakfast isn’t a bad meal. It’s just the wrong meal for the next three hours. This guide explains how the meal before a hard session should differ from your other meals, why the change is mostly about what you remove, and how Avitu rebalances the rest of the day so nothing goes missing.
TL;DR: The meal in the 1–4 hours before a key workout should be carbohydrate-rich - 1–4 g of carbs per kg of body mass (Burke et al., Journal of Sports Sciences, 2011) - and light on the nutrients that slow digestion: fat, fiber and, to a lesser degree, protein. Avitu applies this automatically: meals in the 3 hours before a session marked fuel-to-train or fuel-to-perform get half the protein and fat and no fiber target, with the freed calories swapped for carbohydrates. The protein, fat and fiber you skipped are then moved to your other meals, so your daily totals stay the same.
Key Takeaways
- Carbs up, calories flat. The pre-workout meal doesn’t need to be bigger. It needs a different split: more carbohydrate, less of everything else.
- Fat, fiber and protein slow gastric emptying. They’re the nutrients most linked to gut trouble during hard exercise (Rehrer et al., via GSSI).
- Only key sessions get the treatment. Easy rides don’t need it. Intervals, threshold work and races do.
- Nothing is lost, just moved. The protein, fat and fiber you skip before training go to the meals after it, where they do more good anyway.
Why should the meal before a key workout be different?
A key workout is only as good as the glycogen you bring to it. Guidelines recommend 1–4 g of carbohydrate per kg of body mass in the 1–4 hours before exercise lasting over an hour, with the upper end for long, hard sessions (Burke et al., 2011). A standard mixed meal rarely gets you there.
Hard intervals run almost entirely on carbohydrate. Above threshold, fat simply can’t be oxidised fast enough to supply the power you’re asking for. Your muscles pull from their glycogen stores, your liver keeps blood glucose up, and the quality of your last interval depends on how full both tanks were when you clipped in.
Liver glycogen is the part that’s easy to forget. It drops overnight, and it’s topped up by what you eat in the hours before training. That’s why the pre-workout meal matters more than its size suggests: it’s the last fueling decision you make before the session, and it lands exactly where you need it.
Now look at a typical “healthy” breakfast. It’s balanced by design: plenty of protein, a good dose of (healthy) fat, lots of fiber from oats, seeds, fruit and whole grains. That balance is exactly right for most meals of the day. Before an interval set, it works against you.
Which nutrients cause trouble before hard training?
Fat, fiber and protein all slow the rate at which your stomach empties. In a half-Ironman study, gut problems were more likely with intake of fiber, fat, protein and concentrated carbohydrate (Rehrer et al., summarised by GSSI). Carbohydrate leaves the stomach fastest.
Why does emptying speed matter? During hard exercise, blood flow is redirected from your gut to your working muscles. Whatever is still sitting in your stomach when you start the first interval has to be digested by a gut running on reduced supply. That’s where the cramps, the nausea and the sudden urgent need for a bush come from.
Athletes figure this out on their own. In a 2020 survey of 388 endurance runners, avoiding certain foods before racing was common: 23% avoided high-fiber foods, and that figure rose to 41% among those racing 22 km or longer. Stomach pain or cramps was the most reported symptom when trigger foods were eaten, at 42% (Parnell et al., Journal of the International Society of Sports Nutrition, 2020).
So the three nutrients don’t get equal treatment:
- Fiber is the one to drop almost completely. It gives no fuel for the session and it’s the slowest to move through.
- Fat slows emptying and isn’t the fuel your intervals will use. Cut it back hard.
- Protein also slows digestion, but a moderate dose is useful and well tolerated. Cut it back, don’t remove it.
The American College of Sports Medicine’s pre-event guidance points the same way: a meal relatively high in carbohydrate with some protein, while avoiding large amounts of fiber and fat (ACSM Current Comment, Pre-Event Meals).
Doesn’t cutting protein hurt recovery?
No. What matters for adaptation is total daily protein and spreading it through the day. The ISSN recommends 1.4–2.0 g/kg per day, taken as doses of about 0.25 g/kg (20–40 g) every 3–4 hours (Jäger et al., ISSN Position Stand, 2017). One lighter meal before training doesn’t change your daily total.
The meal after a key session is where protein does its most useful work. That’s when your muscles are primed to repair and remodel. Moving some of your pre-workout protein to the post-workout meal is not a sacrifice. If anything, it’s a better use of the same grams.
The same logic holds for fat and fiber. Your gut still needs its daily fiber, and your hormones still need their daily fat. They just don’t need them in the three hours before you try to hold 330 watts.
This is the key idea behind the whole approach: the day stays the same, the timing changes. Nothing is cut from the day. It’s moved to where it won’t interfere with the session.
How Avitu adapts the meal before a key session
Avitu marks every meal in the 3 hours before a session tagged fuel-to-train or fuel-to-perform as a pre-training meal. Its protein and fat targets are halved, its fiber target goes to zero, and the freed calories are converted to carbohydrates. The meal’s calorie target doesn’t change.
It starts with the fueling strategy you give each activity. There are three:
| Fueling strategy | Use it for | Pre-training window? |
|---|---|---|
| Complete | Most sessions: endurance rides, recovery spins | No |
| Train | Key workouts you’ll push hard in: intervals, threshold, VO2 max | Yes, 3 hours |
| Perform | Goal events where you want to perform at your best | Yes, 3 hours (plus carb loading on the days before) |
Easy rides don’t trigger any change. A Zone 2 spin doesn’t need a special meal, and adapting every meal before every ride would scatter your protein for no real gain. The window only opens for sessions where the quality of the work is the point.
When a fuel-to-train or fuel-to-perform activity has a start time, Avitu opens a 180-minute window before it. Every unlocked meal that starts inside that window is adapted:
protein × 0.5 · fat × 0.5 · fiber × 0 · carbs + (freed kcal ÷ 4)
Take a 72 kg rider with a key session at 11:00 and breakfast at 08:30. Breakfast would normally target 700 kcal: 35 g protein, 22 g fat, 10 g fiber and 86 g carbohydrate. Inside the window, it becomes 17.5 g protein, 11 g fat, no fiber target and 133 g carbohydrate. The meal still totals 700 kcal. Carbs go from 1.2 to 1.8 g/kg, right in the recommended pre-exercise range.
Two practical guards sit on top of this. Meals you’ve already logged and locked are never changed: you can’t un-eat breakfast. And if a meal sits too close to the session (less than 90 minutes before, or less than 60 minutes for a snack), Avitu flags it so you can move the meal or the ride.
The meal card also shows it. A pre-training meal gets a dashed accent in the colour of the session’s fueling intent, so you can see at a glance why its targets look different from the rest of your day.
Where do the removed protein, fat and fiber go?
They move to your other meals. Avitu hands the removed protein, fat and fiber to every unlocked meal outside the pre-training window, and those meals give up the same number of calories in carbohydrates. Your daily calorie and macro targets don’t change.
This is the step most “eat carbs before training” advice skips. If you simply cut protein and fat from breakfast, you’d end the day short on both. If you add carbs without taking them from somewhere, you’d end the day over on calories. Neither is acceptable for an athlete who’s managing a deficit, a surplus or a racing weight.
Avitu solves it as a single trade. Continuing the example, breakfast gives up 17.5 g protein, 11 g fat and 10 g fiber, worth 189 kcal. Those grams are split across lunch, the afternoon snack and dinner, weighted by meal size the same way your regular targets are. In return, those three meals give up 47 g of carbohydrate between them, in proportion to the carbs each one holds.
Here’s what the example day looks like after the trade (rounded):
| Meal | Protein | Fat | Fiber | Carbs |
|---|---|---|---|---|
| Breakfast (08:30, in window) | −17.5 g | −11 g | −10 g | +47 g |
| Lunch (13:30) | +7.0 g | +4.4 g | +4.0 g | −19 g |
| Afternoon snack (16:00) | +4.1 g | +2.5 g | +2.3 g | −9.5 g |
| Dinner (19:30) | +6.5 g | +4.1 g | +3.7 g | −19 g |
| Day total | 0 | 0 | 0 | 0 |
Notice where most of the protein lands: in lunch, the first meal after the session. That lines up with the per-meal dosing the evidence supports. The day still delivers the same fuel, the same protein and the same fiber. It just delivers them in a better order.
There’s one edge case. If every other meal is already locked, or those meals don’t hold enough carbohydrate to fund the trade, Avitu can’t move everything. The pre-training meal still gets its adaptation, and the day’s macro split shifts slightly towards carbohydrate to match. The calorie target never moves.
How do you build a good pre-workout meal in practice?
Aim for a meal that’s mostly quick-digesting carbohydrate, with a modest portion of protein and very little fat or fiber, eaten at least an hour before the session. Most athletes can handle a full meal in that range (ACSM Current Comment, Pre-Event Meals).
A few swaps get most of the way there:
- White over whole grain. White rice, white bread, bagels or low-fiber cereal instead of muesli, rye or brown rice. Just for this one meal.
- Lean protein, smaller portion. A yoghurt or a couple of slices of ham instead of three eggs and bacon.
- Hold the fat. Skip the avocado, the nut butter and the cheese. Honey, jam or banana on toast do the job.
- Peel your fruit. Bananas and fruit juice are easy. A large apple with its skin, or a pile of berries, is fiber you don’t need yet.
Don’t make the pre-workout meal the day you try something new. What sits well is personal, and the survey data shows that clearly: runners’ avoided foods varied a lot by age, sex and race distance (Parnell et al., 2020). Test the approach before normal key sessions, not before your A race.
And once you’re on the bike, the fueling doesn’t stop. A strong pre-workout meal is the first step. The carbs you take in during a long session are the second.
Frequently asked questions
How many carbs should I eat before a key workout?
Guidelines recommend 1–4 g of carbohydrate per kg of body mass in the 1–4 hours before exercise longer than an hour (Burke et al., 2011). For a 72 kg rider that’s roughly 70–290 g. The closer the meal is to the session, the lower in that range you should stay.
Why avoid fiber before training?
Fiber slows gastric emptying and gives no usable fuel for the session. In a 2020 survey of 388 endurance runners, 23% avoided high-fiber foods before racing, rising to 41% for distances of 22 km or more (Parnell et al., JISSN, 2020).
Should I skip protein before a workout?
No, just reduce it. A moderate amount is well tolerated, but a large serving slows digestion. What drives adaptation is daily intake (1.4–2.0 g/kg) spread across doses every 3–4 hours (Jäger et al., ISSN, 2017), so the protein you skip is better placed after the session.
How long before a key workout should I eat?
Most athletes tolerate a full meal 2–4 hours before hard training, and a small carb-rich snack closer in (ACSM). Avitu adapts meals within 3 hours of a fuel-to-train or fuel-to-perform session, and flags meals less than 90 minutes before it (60 minutes for a snack).
Does the pre-workout meal change for easy rides?
Not in Avitu. Only sessions marked fuel-to-train or fuel-to-perform open a 3-hour pre-training window. Easy endurance and recovery rides use the fuel-to-complete intent, which keeps your meals balanced as usual. There’s no performance reason to shuffle your macros before a Zone 2 spin.
The bottom line
The meal before a key workout is not a bigger meal. It’s a differently built one: more carbohydrate, half the protein, half the fat and no fiber target, all inside the same calorie budget. That’s what the sports nutrition literature has recommended for years, and it’s the easiest performance gain most riders are leaving on the table.
The part that’s hard to do by hand is the rest of the day. Every gram you move out of breakfast has to land somewhere else, or your daily targets drift. Avitu does both halves for you. Tag a session as fuel-to-train or fuel-to-perform, give it a start time, and the meals in the three hours before it are adapted automatically. The protein, fat and fiber they give up are redistributed over your other meals, with the working shown in every target. The same day, in a better order. If you’re also running a deficit or surplus, see how Avitu sizes your calorie target around training. The pre-training swap never changes that number.