Do's and Don'ts of Carb Cycling

By Gabrielle Kassel | 20 August, 2019


Sorry, Mudder Nation: Even if you’re training hard for a 5K, Classic, or Toughest Mudder and expending loads of energy on the regular, you probably still can't eat anything you want. But because there are more eating plans than there are ways to get over Everest (read: lots), it can be hard to figure out which eating plan is best for you. We’ve already given you the dirty-deets on intermittent fasting and going veg, and now we’re here with your crib sheet on carb cycling

“Carb cycling is when you plan and manipulate your carbohydrate intake based on your training,” explains registered dietitian and exercise physiologist Jim White, RDN, ACSM, owner of Jim White Fitness & Nutrition Studios. The gist is that you alternate between high and low carb days, so that your higher-carb days fall on your higher-activity days. Why? The theory is that then you get some of the fat-blasting benefits of going low-carb, while still getting enough carbs—your body's preferred training fuel—to power your workouts. “The main goal is simultaneous weight loss and muscle/performance gain,” he says. 

"Bodybuilders, wrestlers, and figure competitors are some of the athletes turning towards carb cycling because in those sports being lean and having a low body weight is an advantage," White says. But is there any benefit for Tough Mudders? It depends on your specific goals. Carb cycling will probably help you lose weight while maintaining muscle mass. And if you’re already on a low-carb diet, switching to carb cycling will likely improve your course performance. But carb cycling is by no means a must for mud-runners. 

Still, if you’re interested in giving it a try, there are some things you need to know to carb cycle effectively. Below, White and Monica Auslander Moreno, MS, RD, LD/N, nutrition consultant for RSP Nutrition, share the main do’s and don’ts. 

Do Count Cals

According to White, “Carb cycling is a labor-intensive process that requires careful tracking of your calorie-intake and macros.” He says the first step is to figure out how many calories you burn every day, known as your Total Daily Energy Expenditure (TDEE). There are some fancy formulas you can use to find it, but TBH Mudders, it’s easier to just use this online TDEE calculator. (Trust us, this is a time to be honest about how active you actually are). 

On lower carb days, your calorie intake should be that number (TDEE) x .75. And on higher carb days, your calorie intake should be that number (TDEE) x .90, White explains. So, for a 2,000 TDEE, a lower carb day would require 1,500 calories and a higher carb day would require eating 1,800 calories total. It’s not a perfect formula, so “it may take some time and experimentation to tweak your exact calorie requirement and need,” he says. 

Do Macro Math

Once you know your daily calorie needs, you’ll divide them between the three macronutrients: carbohydrates, fats, and protein, White says. He recommends figuring out your protein needs first, which he says stay the same on both low and high carb days. 

You should be eating .8 to 1.6 grams of protein per pound of body weight. Where you fall in this range will depend on your activity level, gender, and age, but if you’re training about 60 minutes three or four days a week for your upcoming event, 1 gram per body weight is a good starting point. So, if you weigh 150 pounds, you’re going to aim for 150 grams of protein. 

Next, you’ll need to calculate how many calories that is. “Each gram of protein or carbohydrate contains 4 calories, while fats contain 9 calories per gram,” White says. So, 150 grams of protein equals 600 calories. 

“With the remaining calories, determine 50% and that will be your intake of carbohydrates on higher-carb days. And the remaining calories will be from fats,” White says. “And on low-carb days calculate 20% of your remaining calories, and that will be the amount of calories you consume in carbohydrates on lower carb days.”

If that sounds like a lot of math, well, that’s because it is! A good rule of thumb is that you’ll be getting about 30 grams of carbs on rest days, between 70 and 100 grams on lower-carb lower-intensity training days, and anywhere from 150 to 300 grams of carbs on higher-carb days where you’re weight-training, doing HIIT-style training, or doing CrossFit. “Where you fall in this range on higher carb days depends on what your body can use,” White says. 

Don’t Wing It

In case it isn’t obvious: Deciding to carb cycle is different than actually doing it. “Actually doing it requires an athlete to keep a detailed record of their intake at every single meal and every single day,” Moreno says. 

You can’t simply eyeball an ingredient and guestimate its macronutrient and calorie content—you have to know. Using an app like MyFitnessPal or MyPlate can help with this. 

“You can probably see how this might lead to anxiety, obsession, or disordered eating thoughts and behaviors in a susceptible individual,” Moreno says. So, if you have a history of disordered eating or aren’t down to track, don’t try carb cycling. 

Do Eat Green 

“All humans, athlete or not, carb-cycling or not, should make an effort to include fruits and vegetables daily into their intakes,” Moreno says. However, getting enough fruits and veggies is especially important for folks who are carb cycling or on lower-carb diets.  

White explains: “Eating low carb can result in less fiber intake because there is a lot of fiber in grains, which are reduced on lower-carb diets.” Some carb cycling plans recommend a fiber supplement for this reason, but White says if you prioritize veggies and greens on both your lower-carb days, that shouldn’t be necessary. 

Don’t Go Apesh*t

High-carb day does not equal free-for-all day! Nose diving into sugary drinks, piiles of pasta, stacks of white bread, and cake by the ocean isn’t what dieticians mean by a higher carb day. Rather, on higher carb days, White says, “It is important athletes choose foods that will support their overall health.” Fiber-rich, complex carbohydrates like oatmeal, whole grain bread, brown rice, quinoa, and other whole grains, are great picks on high-carb days, he says. 

Note: This doesn’t mean you can never have bagels or desserts, Moreno says. “If you never allow yourself to eat those foods, that's going to create a very damaging relationship with food over time,” she says. It simply mean emphasizing more nutrient-dense and health-promoting foods on most higher carb days, she explains. 

Do Consult An Expert

“Nutrition, and especially sports nutrition, is so nuanced and individualized that you may want to work with an expert,” Moreno says. They’ll be able to create a personalized plan that takes into account your Tough Mudder training schedule, and ensures that you’re getting all the nutrients you need. 

Gabrielle Kassel is a New York-based fitness and wellness writer and CrossFit Level 1 trainer. When she's not lifting heavy sh*t, playing rugby, or getting downright dirty, she can be found reading memoirs and guzzling cold brew. You can follow her on Twitter or Instagram @gabriellekassel.