What should you eat during a tough endurance event?

One of the perks of being a serious endurance athlete is that you can screw around with impunity. All that training burns big calories, which is why you can do real damage to all-you-can-eat buffets.

In fact, it can sometimes seem like you’re constantly hungry—except during a hard workout or race. In such situations, the fight-or-flight response is triggered and yours sent nervous system into overload and reducing your appetite so you can focus on the job at hand.

The only problem with this little hormonal autofocus is that it can cause you to burn a ton of calories, so if things go on too long—say, more than 90 minutes—you run out of gas.

To avoid running on empty, here’s how to fuel your body during a race.

How your body burns fuel when you exercise

When you exercise, your body can draw fuel from several places:

• Adipose tissue (through lipolysis – breakdown of fat)
• Muscle mass (through proteolysis – breakdown of proteins)
• Carbohydrates (via glycolysis — breakdown of glucose, i.e. blood sugar, which is also stored in muscle and liver cells as glycogen).

When your effort level is low, or when you train ua lower heart rate zoneyour body burns a higher percentage of fat than carbohydrates for fuel. Even really lean athletes have enough fat to last them for a while, so if you’re eating in recovery mode or building a base, nutrition during training isn’t as important (but hydration it still is!).

In fact, many athletes do it on purpose train in a fasted state (i.e. with a lack of glucose). during such training to teach their bodies to better use fat as fuel. But as the intensity of your training increases, so does your body’s reliance on carbohydrates for energy.

If you plan to put in any real effort or if you plan to train for more than a few hours, you’re probably better off loading up on carbs while your body burns through its glycogen stores.

What is glycogen?

Glycogen is basically a reserve source of blood sugar. It is easily converted back into glucose for use as energy. Liver glycogen can be dispersed throughout your body, including your muscles, but muscle glycogen only works for the specific muscle in which it is stored.

Once your glycogen stores are fully replenished, you should have about 90 to 120 minutes of fuel to work with. After that, you “bonk” or “hit the wall”.

If you’ve ever been in the middle of a workout and suddenly felt like even the simplest task was an epic challenge, that’s crazy. Technically, you can still function at that point, because you still have fat and muscle stores to tap into, but you won’t be performing as well.

How to Refuel During a Long Event (60+ Minutes)

1. Start with carbs

Increase your carbohydrate intake for a few days before your raceand since there’s no easy way to know when your glycogen is at 100 percent, hedge your bets by eating a high-carb meal a few hours before it starts.

2. Fuel proactively

Start feeding about 30 minutes after you start rather than waiting for the first signs of fatigue to appear. Why? Because if you wait until you’re tired to refuel, you’ve waited too long. (Our bodies did not evolve to optimize fuel production over 140.1 miles Ironman races and double centuries.)

During extreme exertion, the human body can burn 800 to 1,000 calories per hour. Unfortunately, we can only absorb the eye 360 calories of carbohydrates hour, which means we’re dealing with a diminishing return situation right off the starting line, so it’s important to make a jump on glycogen replenishment.

Since there are four calories in a gram of carbohydrates, 360 calories of carbohydrates is equivalent to 90 grams. But getting those 90 grams isn’t as easy as picking up a jelly donut, because different sugars are absorbed in different ways and at different rates. If you consume nothing but glucose, for example, you will only absorb about 60 grams per hour.

3. Combine types of sugar

There is a trick to maximizing carbohydrate absorption: fructose is absorbed differently than glucose; it needs to pass through the liver. This process can occur simultaneously with the absorption of glucose, so if you consume a mixture of the two, you should be able to absorb more carbohydrates in total – 90 grams per hour.

But while this number is backed by reputable science, don’t take it so hard and fast. Just because you can probably absorb 90 grams of carbs an hour doesn’t mean you can it should. During “shorter” events lasting between one and two hours, you probably won’t need 90 grams per hour, so you can save your digestive system stress and stick to it. 30 to 60 grams per hour.

If you’re going longer, however, it’s best to keep 60 grams per hour as your baseline and add up to 30 grams per hour on top of that, depending on what your system can handle comfortably.

90 grams may seem like a lot of carbs to absorb, but as with most aspects of training, you can increase your body’s ability to handle it. Start with an amount that works for you and then slowly increase your intake. Just remember to experiment during training, not during races.

4. Set reminders

Also, make use of all that fancy data technology you’ve probably invested in. Set a timer on your computer/phone/bionic implant to remind you to drink and eat at regular intervals.

How to hydrate during the event

The science behind feeding events is surprisingly vague, but the science behind events hydration is relatively solid, so you can simplify the feeding part by attaching it.

The amount of your fluid intake should vary depending on your sweat rate, which, according to the American College of Sports Medicine, can vary from 8 to 67 ounces per hour during the event. Finding the perfect hydration level can take time, but cyclists usually start with around 24 ounces per hour. That’s about the amount you’ll find in a standard water bottle, making it easy to keep track of.

Should you use a sports drink?

You might be tempted to fill that bottle with sugar sports drink so you can remove your nutrition and hydration at the same time. There’s a small chance this might work for your unique physiology, but chances are it does hypertonic (more concentrated than blood) nature of that delicious drink will not be absorbed efficiently.

This can lead to stomach upset or, as happens in many cyclocross races, vomiting. You’re better off with a hypotonic (less concentrated than blood) drink with less sugar. Such solutions tend to absorb more efficiently and effectively.

A good sports drink will offer carbohydrates as a combination of fructose and glucose. One serving Beachbody Performance Hydrate contains 10 grams of carbohydrates, so if you drink four servings in an hour, that’s 40 grams, which means you’ll only need to eat 20 to 50 grams (or about 80 to 200 calories) of carbohydrates from food in that hour.

You can always try to get all your carbs in liquid form, which is not uncommon during pregnancy triathlonbut this presents several problems. First, if you stick with a hypotonic mixture, that’s a lot of water.

Second, consuming just one thing for hours on end while suffering mentally and physically is a recipe for taste fatigue—where you develop such a distaste for food that your exhausted, exercising brain actively prevents you from eating or drinking. By mixing liquids and solids, you have a better chance of avoiding taste fatigue and maintaining your appetite.

What types of food should you eat?

Anything that tastes good and consists primarily of carbohydrates will probably work. You want to absorb those sugars quickly high-glycemic foods (ie those that raise blood glucose quickly) are great in this situation.

Some popular options include bananasmelon, other fruits with little fiber and mini pretzels. (Three to four hours after a particularly difficult event, I also enjoy an eight-ounce can of Coke. Hooray for carbs and caffeine!)

But if your event is going to be consistently taxing or disruptive to your system – triathlon and marathons come to mind — gels and chews are easily digestible feeding options. Again, take care of it read the ingredients to check the sources of sugar.

The triathlon swimming dilemma

You Ironman folks out there are probably scratching your heads, considering it’s pretty heavy fuel while you’re swimming. And by “difficult” we mean impossible.

So make sure you’re fully fueled and hydrated before you start your race and focus on refueling the moment you hit the road terra firma. Keep a full bottle either next to your bike or in your transit bag to sip as best you can while changing.

When it comes to diet, it’s up to you to determine how much you can tolerate and/or accept. If you can chew a chew or two during the transition without slowing down, great. Otherwise, consider feeding during the first few kilometers on the bike. Keep in mind that it’s easier to eat when you’re cycling than when you’re running, so don’t fall behind here.

However, suddenly filling your gut can lead to GI issues, so it’s important to learn what your intake limits are here. Treat this transition fueling like any other part of your training.

A word about proteins

Doc protein is instrumental after the event, it should play a very small role feeding during the event. Your goal is to replenish glycogen as quickly as possible, and protein slows absorption.

An exception is a multi-stage race. In this case you want to keep protein turnover (muscle synthesis and breakdown) in balance as much as possible, so low protein during such an event is a good idea. Just keep carbs first in your diet and experiment with protein during training to see how much you can tolerate.

Final Word: Do Whatcha Like

While all of these tips give you a great starting point for event nutrition—or, hopefully, a way to fix a problem with your current method—keep in mind that personal taste and biology go a long way in determining what foods are right for you. Never, ever experiment during a race. But when training, don’t be afraid to try different foods, in different amounts, in different ratios of solid to liquid.

Also, don’t be afraid to grab the samples offered at the race registration booths (for later use), or pounce on your friends when they have something you’ve never tried.

Find the intersection of what works scientifically and what works personally. Once you figure it out, you’ll be unstoppable.