Protein Before a Workout or After? Here's What a Dietitian Says

If you're looking to build muscle, the question of when to eat protein around a workout (before? after? during?) becomes an important one, especially because it seems like everyone has their own routine. You might see some people shaking up a protein drink between reps at the gym or munching on a bar right before or after their workouts. Protein is essential if you're trying to build muscle, but when should you consume it to maximize your gains?

Whether to have protein before or after a workout comes down to two factors: muscle breakdown and possible stomach upset, according to registered dietitian Michele Fumagalli. You want to prevent both of them for different reasons. While some muscle breakdown is necessary to get stronger (more on that below), the goal is to ensure that your body has the nutrients to build those fibers back. On the gastrointestinal side, it's important to remember that protein is a more complex macronutrient and therefore more difficult to digest. It can cause stomach discomfort if eaten too soon before your workout.

But before we get into the details, let's start with some basics.

People associate protein with muscle building because of what happens when you don't eat it, Fumagalli explains. The way you build muscle is actually by breaking it down, creating tiny tears in the tissue (which happens during your workout), then rebuilding it bigger and stronger. But that's only possible if you give your muscles the nutrients they need to grow. Protein is the compound that does that best because your body breaks it down into amino acids, compounds that repair your muscle tissue. When your body doesn't have protein available, the muscle tissue can't rebuild and may start to break down or atrophy.

That brings us to the timing question. You can get pretty deep into the details of when and what exactly to eat before a workout, but here's a good rule of thumb: the closer you get to your workout, the more you should stick with foods that are easily digestible.

"Two-and-a-half to three hours before a workout is kind of when you want to have your last meal," Fumagalli says — a full meal with carbs, protein, and fat. About an hour out from a workout, if you're hungry, she says you should stick with carbs and a small amount of protein, like a granola bar or a banana with a tablespoon of peanut butter. If you're hungry right before the workout — say, half an hour out or less before you want to start exercising — you should stick with straight carbs. Fumagalli suggests applesauce: sweet and easy to digest.

Why not load up on protein right before a workout? It has less to do with muscle gains and more to do with workout discomfort. Protein is harder to digest than carbs, so your body sends blood to your stomach to help break it down. But when you exercise, that blood gets diverted to your muscles "because those are what we're exhausting and we're using," Fumagalli says. Having heavy, protein- and fat-rich foods in your stomach when the blood gets called away can cause stomach upset, making for an uncomfortable and often underperformed workout, which can hurt your muscle gains.

As for protein after your workout, Fumagalli says that's essential for preventing muscle breakdown, especially if you haven't eaten for over three hours beforehand (and even if you're not hungry). Throw in some carbs, too, to replenish your supply of glycogen (stored glucose, which your body gets from carbs) that got used up during the workout. But, Fumagalli adds, the post-workout protein isn't as necessary if you ate more recently. "If you had a premeal maybe two hours, two-and-a-half hours prior, your body's using that protein and the carbohydrate that you ate to fuel yourself during the workout and recover afterward," she says.

In other words, the protein and carbs you eat afterward will supplement that process but aren't quite as crucial as they would be if you'd done a fasted workout. In the latter case, it's more important to eat something in order to prevent muscle breakdown. A 2003 study showed that both muscle synthesis and muscle breakdown spike an hour and a half after a workout, meaning that your muscles are primed for growth but can also go the opposite way without proper refueling.

The main takeaway: you're good to eat protein before a workout as long as it's far enough in advance to avoid gastrointestinal stress. Aim for an hour out, at the latest. The post-workout protein will be more crucial, particularly if you do a fasted workout (not eating for three or more hours before, or working out first thing in the morning without breakfast). Whatever you do, remember that these are just two snacks out of a full day of eating, Fumagalli says. Eating a healthy balance of carbs, protein, and fat throughout the day, not just around a workout, will also boost your muscle gain and keep you healthy and energized.

Wondering what kind of protein is the best? Fumagalli recommends protein shakes if you need a quick, convenient option, but she says natural sources of protein (such as chicken or tofu) are best, if available. Pick the protein and workout timing that work for you to maximize your muscle-building goals.