A triathlon is the somewhat masochistic succession of swimming, cycling, and running. Training in each of these three disciplines is obviously necessary, but people often talk about the 4th discipline of triathlon: nutrition.
Eating well is important for any physical activity, but in triathlon, it becomes critical to make sure everything “goes down well” (no cramps) over short distances, or simply to have enough energy over longer distances.
Nutrition is very personal, but I wrote this guide because my experience as a triathlete can inspire both beginners and more experienced athletes. There is always more to learn about nutrition!
In brief
- What matters is the duration of the effort, not the distance.
- Before swimming: an easy-to-digest meal about 2 hours beforehand, then only a little liquid.
- For longer distances: aim for 60 to 90 g of carbohydrates per hour, especially on the bike.
- In the heat or beyond 2 hours, drinks should contain electrolytes.
- You train your stomach and test everything in training, never on race day.
Factors to consider
It starts with swimming!
A triathlon starts with swimming (obviously!), but for many people, swimming causes food-related abdominal cramps. The most common strategy is to eat something that is easy to digest (e.g., oatmeal) about 2 hours before the effort, then have only a little liquid before the start.
The swimming portion is fairly short, and you have enough glycogen to complete it. Races generally start early, and my personal routine is to eat a Zenit chocolate and coffee square in the car with a fruit smoothie.
Duration of the effort
People often think in terms of distance, but what really matters is time. A beginner who does a sprint in 2 hours will need a completely different strategy from an experienced athlete who finishes in a little over an hour.
The same goes for an off-road triathlon, which adds 30 to 60 minutes to a sprint event. And let’s not even talk about Ironman events lasting more than 12 hours!
This is where you need to try things out in training, along the lines of: “OK, I can do 2 hours of sustained effort with 2 bottles and 3 snacks.”
Temperature
It’s too hot for marathons in July, but the heat doesn’t prevent triathlons from taking place. In the heat, you’ll obviously drink more, but your stomach may not function as well. Doing a sprint in the heat without electrolytes is possible, but for longer distances, it is strongly recommended that your drinks contain electrolytes.
Your tolerance for food
There's mental strength, but we could add stomach strength. When I started, I got abdominal cramps during the run whenever I swallowed anything. Now I can eat a Greek salad and go running right afterward without any problem.
The trick? I gradually trained my stomach to better tolerate food while moving. It may seem trivial, but it is practically impossible to finish a long-distance triathlon if you can't eat properly during the race.
What will be available along the course
You want to get used to consuming what will be offered along the course. I'm a big fan of natural foods, but aid stations typically serve commercial products. It's better to get used to the sublime taste of warm Gatorade... LOL
My formula by distance
Short distances
The number one goal is to avoid cramps while still having enough energy for the final minutes of the event.
Sprint (750 m - 20 km - 5 km, about 1 hour)
One Zenit energy square in the car + a smoothie. Sports drink on the bike (I rarely finish my bottle), no water during the run.
Olympic (1500 m - 40 km - 10 km, about 2 hours)
One or two Zenit squares in the car + a smoothie. Sports drink on the bike (I almost always finish my bottle) and a bag of Zenit energy balls "just in case." Water or sports drink about every 10 minutes during the run (every other aid station).
Long distances
The number one goal is to eat as much as possible as long as it sits well. You expend more energy than your gut can absorb, and a lack of calories can have as much impact as muscle fatigue.
Half Ironman (1.9 km - 90 km - 21.1 km, about 5 hours)
One or two Zenit squares in the car + a smoothie. At least 2 bottles of sports drink on the bike and half a Zenit energy ball every half-hour, whether I'm hungry or not. I take every sports drink at the aid stations during the run.
Ironman (3.8 km - 180 km - 42.2 km, over 10 hours)
A good breakfast + a smoothie 2 hours before the race + a bag of Zenit energy balls 15 minutes before the start. One bottle of sports drink per hour on the bike and half a Zenit energy ball every half-hour, whether I'm hungry or not, plus whatever looks good at the aid stations. During the run, I take every sports drink at the aid stations and take the time to eat snacks.
The nutritionist's advice
For efforts lasting more than 2 h 30, current recommendations aim for 60 to 90 g of carbohydrates per hour, combining different sources of sugar (glucose and fructose) to improve absorption. A 750 ml bottle of sports drink provides about 45 g of carbohydrates; to reach these targets, solid snacks are added, especially on the bike, where the stomach tolerates food better. As Jean puts it so well: take it gradually and test during training. – Danielle.
Conclusion
Nutrition is very personal, and it is up to you to find your formula. Try things!
You may realize that you do not need to drink for events lasting less than 45 minutes, or that very sugary products give you a “sugar crash.” That is why I like Zenit products: made with simple ingredients, they give me energy that works for me.
But when I say “try things,” I mean BEFORE the race. On race day, stick to your plan.
Frequently asked questions
What should you eat before a triathlon?
An easy-to-digest meal, rich in carbohydrates and low in fat and fiber, about 2 hours before the start (oatmeal, smoothie, energy bar), then only a little liquid before the swim.
How many carbohydrates per hour during a half-Ironman or an Ironman?
Aim for 60 to 90 g of carbohydrates per hour, combining sports drinks and snacks, and gradually train your stomach.
Should you eat during a sprint triathlon?
For a sprint lasting about 1 hour, a sports drink on the bike is generally sufficient. The pre-race meal provides most of the energy.
By Jean Thibaudeau, experienced triathlete
Revised and updated in October 2026 by Danielle Dubois, nutritionist.
References
- Thomas DT, Erdman KA, Burke LM. Position of the Academy of Nutrition and Dietetics, Dietitians of Canada, and the American College of Sports Medicine: Nutrition and Athletic Performance. Med Sci Sports Exerc. 2016;48(3):543-568. PMID : 26891166
- Jeukendrup A. A step towards personalized sports nutrition: carbohydrate intake during exercise. Sports Med. 2014;44(Suppl 1):S25-S33. PMID : 24791914
- American College of Sports Medicine; Sawka MN, Burke LM, Eichner ER, et al. American College of Sports Medicine position stand. Exercise and fluid replacement. Med Sci Sports Exerc. 2007;39(2):377-390. PMID : 17277604