Here's Exactly How to Carb Load — Straight From a Dietitian

POPSUGAR Photography | Diggy Lloyd
POPSUGAR Photography | Diggy Lloyd

Carb loading can be extremely confusing, especially if you're new to sports nutrition — do you just eat a bucket of pasta the night before a half-marathon and hope for the best?! How do you properly increase these necessary macros without sabotaging your diet or messing with your metabolism? What day do you start the loading, and most importantly, when do we get spaghetti?

We consulted Lori Zanini RD, CDE, who is an expert in all things carbohydrates and blood-sugar levels. The creator of For the Love of Diabetes online training program and dietetic brains behind the Tone It Up nutrition program knows a thing or two about optimizing carb intake before intense and sustained exercise without compromising your health.

Why Is It Important?

Short answer: your body needs the extra energy.

Skimping on the carbs before an endurance event (something that will last more than 90 minutes) will leave you feeling tired, sore, and struggling to concentrate and could lead to even worse problems. "The goal of carbohydrate loading is to utilize glycogen stores in the muscle and liver," Lori told POPSUGAR.

"This is the long-term carbohydrate storage where the body taps into in order to keep energy levels stable and to provide enough energy for long-duration performance." Read: this is the extra fuel you need to complete your race or event. Don't let your body run on empty! "By consuming enough carbohydrates prior to a long run/endurance event, athletes are setting themselves up for success rather than fatigue and impaired concentration during their event."

Is It Safe For Everyone?

Short answer: yes.

"If an endurance athlete does not have diabetes or prediabetes, then it is fine to carb load," said Lori. "The insulin their body produces will naturally keep blood sugar levels regulated." If you fall into the diabetic/prediabetic category, it's best to consult your doctor or dietitian before adding in extra carbohydrates. "Carb loading is also effective and beneficial for those with prediabetes/diabetes as long as they have good blood sugar control overall," she said. "And they will want to pay extra attention to choosing high-fiber carbs and this with a lower glycemic index."

What's the Timeline?

Short answer: two days before your race.

Surprise! A huge bowl of pasta the night before is actually not the ideal time frame for carb loading. "Optimal carbohydrate loading period is between 36 to 48 hours before a race," Lori told POPSUGAR. This means either dinnertime two nights before your race or a big breakfast or brunch two days prior.

Here's an exact method: the "carbohydrate loading technique consists of three to seven days of a high-carbohydrate diet (with an average of 60 percent of calories coming from carbohydrates), combined with one or two days of reduced exercise volume," Lori explained.

So a good rule is to give yourself a week — not just a night — of increased carbohydrate intake to help your body adjust. This all happens while you're tapering (reducing your exercise) for the last two days before your endurance event.

"According to the Academy of Nutrition and Dietetics, exercise taper and a carbohydrate-rich diet of seven to 12 grams of carbohydrates per kilogram of body weight per day can normalize muscle glycogen levels within 24 hours, while extending this to 48 hours can achieve glycogen supercompensation (where muscles are able to hold a greater amount of glycogen than they normally would be able to)."

The Dos and Don'ts


  • Test different carb sources. Not everyone digests pasta in the same way. "Trial carbohydrates sources before practice to monitor tolerance and comfort to different carbohydrate sources," said Lori. This will help you "create the best plan for you before a race."
  • Increase carb content based on your weight. "In preparation for events that are 90 minutes or more of sustained/intermittent exercise, consume 10 to 12 grams per kilogram of bodyweight of carbohydrates per day." For example, if you weigh 60 kilograms, eat 600 to 720 grams of carbohydrates while carb loading.
  • Pair with protein. Lori suggests balancing the carb load with some protein to help nourish your muscles and keep you full.
  • Eat smaller meals vs. one big one. "During a carbohydrate-loading phase, small, frequent carbohydrate-rich meals combine with lean proteins will be best compared to big portions of carbohydrates at one or two sittings," she told POPSUGAR.
  • Choose the right carbs. The healthiest way to carb load? "Focus on low/medium glycemic index choices during the carbohydrate-loading phase," she said. This includes "oatmeal, sweet potatoes, fruits, etc." She notes that "As you get closer to the hours of competition [i.e., race day], lower-fiber carbohydrate choices may be better tolerated and help top off energy stores."


  • Try anything new before race day. This is a cardinal, age-old rule. A tale as old as time, if you will. "Don't try a new fuel source before an important race or tournament," said Lori. "Make sure to trial different foods ahead of time and see which works best for your body and particular sport."
  • Load up on high-fat, high-protein, or high-fiber foods. "Don't consume foods high in fat, protein, or fiber before the race as this may cause gastrointestinal issues during the event."
  • Use sugar as your carb source. Quality over quantity, you guys! "Don't just load up on sugar," Lori warned. "While ensuring athletes are meeting carbohydrate needs, our goal is to still focus on consuming quality fuel sources such as quinoa, oatmeal, whole-wheat pasta, sweet potatoes, and fruits."

Race on!