Nutrition

How Many Carbs Do You Need for Triathlon Training?

Carbohydrates have gone from “nice to have” to essential for endurance performance. Over the last century, research has shown not only that carbs are a primary fuel during hard training, but that taking them in during longer sessions can help you go further, feel stronger, and recover better. More recent work has fine-tuned the advice, so today’s recommendations are based on what matters most in triathlon: how long you’re working and how hard you’re going. Below, you’ll learn how much carbohydrate to aim for based on session length, when a carb “mix” matters, and how to train your gut so fuelling feels easy, not risky.

When you’re training for triathlon, carbs are basically your “fast fuel.” The longer and harder you go, the more your body relies on them and the more you benefit from topping them up during the session.

The modern advice has shifted from one generic rule to a sliding scale based on session length (and intensity). Getting this right helps you avoid the mid-session slump, hold pace on tired legs and recover faster for your next workout.

A Simple, Evidence-Based Carb Guide During Training

• 30–75 minutes (hard effort): small amounts of carbs can help – sometimes even a quick carb mouth-rinse can boost performance. Practically, if you feel flat, a few sips of sports drink or a small gel can help.
• 1–2 hours: aim for about 30 g carbs per hour (e.g., 1 gel/hour OR 500–750ml sports drink – check the label)
• 2–3 hours: aim for about 60 g carbs per hour (e.g., 1 bottle sports drink + 1 gel/hour or a higher-carb bottle mix)
• >2.5 hours: aim for about 90 g carbs per hour but only if you use the right type of carbs (more on that below). Look for products that list glucose/maltodextrin + fructose (or “glucose-fructose”) on the label.
• Start fuelling early (within the first 20–30 minutes) on any session longer than 75–90 minutes, waiting until you feel empty usually means you’re already behind.

If your session is very easy / low intensity, you’ll burn carbs more slowly, so those numbers may need to come down a bit.

When The Carb Type Matters

Single vs “multiple transportable” carbs (in normal person language)

Think of your gut like a doorway system.

Single-transport carbs = one main doorway

If you’re using one main carb type (like glucose or maltodextrin), it mainly uses one gut transporter. That transporter can get “maxed out” around ~60 g/hour  which is why for many years 60 g/hour was seen as the upper ceiling.

Multiple-transport carbs = using two doorways at once

When you combine glucose (or maltodextrin) + fructose, you’re using different transporters, so more fuel can get absorbed and used. This is what “multiple transportable carbohydrates” means. This is why many athletes feel better (and often perform better) on higher intakes when they use a glucose/maltodextrin + fructose mix, more gets absorbed, and less sits in the gut. That matters most when you’re trying to hit higher intakes (like ~90 g/hour) for longer sessions.

Why “Train The Gut” Matters (and what it actually means)

A lot of fuelling problems aren’t fitness problems they are gut tolerance problems. Because absorption can be a limiter, it’s recommended you practice your race-fuelling strategy in training to reduce GI discomfort and potentially increase your ability to absorb carbs.

There’s also evidence that a higher-carb approach in training for several weeks can increase exogenous carb oxidation (basically, your ability to use the carbs you consume while exercising).

How To Actually Do It

• Pick one session per week (usually a longer ride/brick)
• Start with an amount that feels easy (e.g., 30–40 g/hour)
• Aim to practice fueling every 10–15 minutes rather than taking a big hit all at once (it’s easier on the stomach).
• Build gradually every 1–2 weeks toward your target (e.g., 50 → 60 → 75 → 90 g/hour)
• Big jumps (e.g., 30 → 90 g/hour overnight) are the fastest way to get stomach issues so build up gradually and keep the same products during practice.
• Keep it consistent so your gut learns the routine

Quick Rules To Remember

• Short & hard (<75 min): optional carbs, but useful if you fade
• 1–2 hours: 30g carbs/hour
• 2–3 hours: 60g carbs/hour
• >2.5 hours: up to 90g carbs/hour with a glucose/maltodextrin + fructose mix
• Practice in training to “train the gut” and make race-day fueling feel normal.
• Most athletes can take in more carbs on the bike than the run, so do the heavy lifting with fuelling on the bike and keep the run simpler.

Point to note: Very concentrated drinks/solids can reduce fluid absorption, so your carb plan should still work with your hydration plan. The best plan is the one you can repeat comfortably, practice it, refine it and make it automatic.

Sources: Jeukendrup, A. (2014). A step towards personalized sports nutrition: carbohydrate intake during exercise. Sports medicine, 44(Suppl 1), 25-33.