What to eat before a run

On the surface, exercise can seem pretty straightforward. If you run, you simply choose a route, pull on your sneakers, and go. The best running watches can even pull the stats so that you don't have to. But when it comes to choosing what to eat before a run, it’s easy to get distracted reading about carb-loading dinners, power snacks, and hydration bottles. These fueling techniques can seem overwhelming, yet they could mean the difference between success and failure for your next 10km, half-marathon, or marathon. 

Whether you prefer hitting the tarmac or hopping onto one of the best treadmills, not only do you have to be aware of when and what to eat pre, during, and post-running, but you also need to keep an eye on your hydration levels. That’s why in this feature Live Science asked the experts to cut through the noise and give us their tips for success.

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What should you eat before a run?

You don’t need to run on empty to experience an effective run. In fact, researchers from the University of Limerick have proved that pre-exercise eating improves athletic performance. Eating before running is important to ensure your muscles have enough fuel to get through the workout, dietitian and Boston Marathon runner Alicia Galvin told Live Science. "If you’re eating less than 30 minutes before you run, aim for something liquid so it can easily digest, such as a sports drink. Or if you plan to eat two to three hours before a run, aim for a small easy to digest snack, like a rice cake with two teaspoons of peanut butter, a banana with honey, or a few homemade energy balls made with nut butter."

Functional medicine nutritionist Karin G Reiter added: "It’s best to avoid heavy foods and foods that are fatty and fried before a run, because it will take the digestive system a while to digest it which might make you tired, heavy and sluggish. Avoid fried foods, meat, nuts - all these are better post-run."

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Some people might want to have a little java jolt before their run to put a spring in their step. But a caffeine hit doesn’t work for everyone. Reiter said: "Caffeine for some can be a good option before a run. Some people feel like caffeine is not digested well in their system and therefore they should not insist on it before a run." 

How far in advance should you eat before a run?

You don’t want to run on a full stomach, so eat two to four hours before a workout. A large meal before your workout could make you feel bloated before your run. The reason why you need a break is that after you’ve eaten, your body goes into overdrive so you don’t need to put it under further pressure. 

Each macronutrient (protein, carbohydrate and fat) that you’ve eaten is processed differently by the body. For instance, with carbohydrates, saliva and the enzyme salivary amylase start to break down carbs in the mouth. 

The breakdown continues in the small intestine, where it is broken into glucose, galactose, and fructose, and absorbed into the bloodstream, and carried to organs. Then the remaining undigested carbohydrate, which is mainly fiber, enters the large intestine where the bacteria feed on it through the process of fermentation. 

"This process can produce the by-product of gas, which is why you may experience gas and bloating after an extremely fibrous meal," says dietitian Elizabeth Gunner.

In the case of protein, chemical digestion begins in the stomach, where it is absorbed as amino acids, and used by the different tissues in the body, and with fat, the gallbladder and the pancreas help break it down in the small intestine. "Fatty acids are passed through the lymph system and then to the entire body through our bloodstream. This fat is used for various cell functions such as energy and growth," Gunner says.

You feel the effects of sugar the fastest because sugar in food is quickly absorbed. "Fat, however, is more slowly absorbed and therefore affects blood sugar levels to a lesser extent," adds Gunner.

What should you eat after exercise?

Not eating anything post-workout could interfere with recovery and muscle building. "The composition of post-workout meals is slightly different from pre-workout meals," says Gunner. "Post-workout meals should include mostly protein to stimulate muscle-protein synthesis; a moderate amount of carbohydrates to replenish glycogen stores, and little to no fat as fat can slow down digestion and cause a slower uptake of other nutrients."

When you should eat depends on your fitness goals Gunner adds: "If your goal is to gain weight, you should consume food within 15 to 20 minutes, and if your goal is to maintain or lose weight, wait for 45 to 60 minutes before you eat."

Alicia Galvin said that a healthy post-workout snack could include chocolate milk, a protein smoothie with fruit, peanut butter and jelly sandwich, or protein bar. "They are all good options post run to refuel and recover," said Galvin.

Hydration is also key. You need to drink fluids pre, post and mid-workout. Galvin explains that: "Dehydration can cause loss of performance, muscle cramps, increased muscle soreness, fatigue, heat exhaustion, and increased time to recover."

After an intense workout you need to consider your sweat rate and how much liquid you have lost. "You need to drink 16 to 24oz of fluid for every pound lost, so weigh yourself pre and post workout to keep track of weight change," says Galvin. If you’re working out for more than two hours, Galvin also suggests you have an electrolyte drink to refuel working muscles.

If you want to work at your optimum, Gunner recommends calling in the professionals. "I would highly suggest working with a registered dietitian or another qualified healthcare professional to receive specific, individualized advice to best support your overall health."