A nutritionist explains the purpose of carb-loading and why it’s useful for some activities and not others.
From marathon-eve pasta parties to pre-race bagels and bananas, consuming extra carbohydrates before an endurance event is a time-honored tradition and best practice for athletes who want to optimize their performance and avoid hitting the dreaded wall. But does it make sense to carb-load before a particularly tough strength training workout, too?
We spoke with Jaclyn Sklaver, MS, CNS, LDN, sports nutritionist and founder of Athleats Nutrition, to better understand why endurance athletes fuel the way they do, and if the same logic applies to lifting heavy.
Why Do You Carb-Load?
Of the three macronutrients (carbohydrates, fat, and protein), carbohydrates are most easily metabolized to create glucose, the body’s primary energy source. Glucose fuels everything from our brain and bodily functions to basic daily activities and, of course, exercise. Any excess glucose not immediately used by the body is stored as glycogen in the muscles and liver. When glucose is unavailable (when you haven’t eaten in a while or you’ve burned through your glucose supply), the body can tap into glycogen stores for energy production.
The purpose of consuming higher-than-normal amounts of carbohydrates, a.k.a. carb-loading, is to bolster glycogen stores. Athletes typically carb-load in preparation for long endurance events so that they have an uninterrupted energy supply up until when they reach the finish line.
According to Sklaver, carb-loading is appropriate for bouts of sustained physical activity lasting longer than 90 minutes, like marathons, triathlons, and cycling events. “You want to go into this race completely loaded up on as much glycogen as possible,” she says. “You will also need to replenish your fuel source throughout the race.” (That’s where those easy-to-digest gels and gummies come into play.)
The typical carb-loading strategy, she explains, is to begin increasing your carbohydrate intake about three days before your event, aiming to consume 7 to 10 grams of carbohydrates per kilogram of bodyweight. A 150-pound person would temporarily up their carbohydrate intake to between 475 to 680 grams of carbohydrates per day.
Should You Carb-Load for Strength Training?
What about those grueling strength training sessions that feel like marathons? Could the same strategy help you build muscle tissue or score a new one-rep max?
No, says Sklaver. “We don’t need to carb-load to lift, that’s for sure,” she says.
Most strength-training workouts run anywhere between 20 to 60 minutes—well under the 90-minute mark when glycogen stores typically become depleted. And even if you do spend hours at the gym, strength training typically includes short bursts of activity interspersed with rest periods, not the long, sustained effort of an endurance workout. For those reasons, the average strength training workout won’t deplete your glycogen stores the same way that a marathon or triathlon will.
In a systematic review of carbohydrate intake and resistance training published by the journal Nutrients, the authors explain that strength training exercise is intermittent, often with 1 to 3 minutes of rest after each set of a movement. These rest periods allow the aerobic system, which can be fueled by fatty acids rather than carbohydrates, to continue a considerable portion of a workout’s total energy expenditure. That means your body doesn’t need to tap into glycogen for strength training alone, so you don’t need to build up glycogen stores by carb-loading.
How Do You Fuel Up for a Strength Training Workout?
While carb-loading for strength training isn’t necessary, adequate carbohydrate consumption is. “I think for people who are just starting to focus on their nutrition, the number one thing to focus on is, are you getting in enough carbs throughout the day to fuel your brain, your body, and your workout? If so, you can evenly distribute those carbs throughout the day and be just fine,” Sklaver says.
Just how many grams of carbohydrates you need per day will depend on your body composition and activity levels, but, according to Sklaver, most people who are working a traditional desk job, commuting by car, and exercising for about an hour a day need between 1.25 and 1.5 grams of carbohydrates per pound of body weight. If you have a more physically-demanding job or run all of your errands on foot, your requirements may be higher.
A slightly more advanced dietary tactic is to concentrate your carbohydrate intake around your workouts. A good rule of thumb, Sklaver says, is to eat 25 percent of your daily carbohydrate allotment 1 to 4 hours before a workout and another 25 percent within 45 minutes of finishing your workout. The remaining 50 percent of your carbohydrates should be evenly distributed throughout the day. This approach to nutrient timing can also be beneficial for people experiencing insulin resistance or hypothyroidism, Sklaver says. “In those cases, you want to focus your carbs mostly around your workouts because that’s when they’re going to get used the best and that’s when you need them the most,” she says.
More on fueling for resistance training:
Are You Getting Enough Protein? Here’s What the Science Says
What are the Best Sources of Carbohydrates?
Sklaver’s number one tip for choosing carbohydrate sources is to consider their nutritional content. Avoid simple carbohydrates like candy, baked goods, and sugary drinks that have no redeeming nutrients.
Unlike a professional athlete, the everyday person or fitness enthusiast doesn’t have the “luxury of hundreds and hundreds of grams of carbs per day,” Sklaver says. Their carbohydrates have to keep them feeling satiated, deliver vital nutrition, and fuel their brains and bodies. “So, if you’re only getting 150 carbs a day, I’m not going to tell you to have 50 of your carbs from fruit and that’s it, because you’re going to be hungry,” Sklaver says. “I want you to have a potato or a rice bowl after your workout. Something that’s substantial.”
Here are a few more options to consider if you need inspiration:
- Whole-grain toast with peanut butter and banana
- Roasted chickpeas
- Greek yogurt with granola and berries
- Oatmeal with sliced fruit
- Savory fonio porridge with sauteed greens and mushrooms
- Baked sweet potato
- Grain bowl with quinoa, vegetables, and chicken
- Rice, bean, and vegetable burrito with a whole wheat tortilla
