If you’re an athlete, you probably have noticed that what you eat impacts your performance, for better or for worse. A lot of us are focused on what to eat to go harder, stronger, or longer in our respective sports but there's so much information out there on nutrition and not all of it is correct, or even helpful. Some of it is just plain wrong, but most of it is nuanced and needs to be understood in context.

I reached out to some leading sports nutritionists to discuss common myths floating around out there and to get the correct advice to set the record straight. 

Myth 1: Carbohydrate Intake is Based on Weight during Exercise

Carbohydrates are the best fuel source when it comes to endurance sports, but how do you know how much you need per hour? Sports Nutritionist Anne Guzman notes that during exercise, many athletes think that carbohydrate intake is based on body weight, but this is not the case.
Anne says, “Carbohydrate intake is based on grams consumed per hour, since intake is based on the rate of absorption through the intestines, which does not seem to differ based on your body weight. Simply put, whether you weigh 130lbs or 180lbs you should still follow the recommended intake from 30-100g per hour, depending on the duration and intensity of your training." 
As an ultra-endurance mountain biker, my intake on the bike is usually a combination of GU gels, Chews, and Roctane Energy Drink mix. I aim for 75-100g/hour during races. Always make sure to drink some water with Energy Gels and Chews to help digestion. In a race, I put my gels in a flask and add water so it’s about a 75%/25% combo of gel to water.

Myth 2: Losing Weight Will Always Improve Performance 

Being an endurance athlete makes this one complicated. It's true that there are performance gains in endurance sports when you are lighter, but that can come at a high cost. Awareness has grown around Relative Energy Deficiency in Sport (RED-S) - a situation in which an athlete has insufficient energy intake relative to the amount of training being undertaken. Symptoms of RED-S include lower bone density (and resulting stress fractures) and hormonal disruptions as the body goes into "energy-saving mode."
Lori Russell, a Registered Dietitian with board Certification as a Specialist in Sports Dietetics observed that that she often sees athletes that believe they must be in a calorie deficit to lose weight and perform well. She says, “This makes sense for a normal person, but when performance is a priority, the body needs something to burn! More calories are often needed to improve energy levels, output capacity, and build muscle.” She recommends, “stop focusing on cutting calories and start adding quality to meet your performance needs.”
I’ve experienced trying to restrict calories hoping to lose weight only to be unsuccessful. When I’m focused on choosing plentiful healthy foods instead of restricting and going hungry, I’ve seen the biggest improvements in my performance. If you lose too much weight, there is a point where your immune system weakens and you don’t recover as well. 
The bottom line: Focus on healthy eating habits first, having good energy and consistent workouts, and weight loss third.

Myth 3: Carbs are Bad

Let's face it, carbohydrates have gotten a bad rap, while protein is often glorified. Not all carbohydrates are the same, though. Refined carbohydrates are often the culprits that cause unwanted spikes in energy or body weight. In her book Nourish, Brenda Davis, RD says that “refined carbohydrates are carbohydrate-rich foods that have been stripped of most of their beneficial components by food processing techniques before we eat them. There are two main categories of refined carbohydrates – sugars and starches. When we extract the sugars and starches from plants, we leave behind much of what is of value to human health. There is overwhelming evidence that excessive intakes of refined carbohydrates are linked to a laundry list of adverse health outcomes.”

Refined carbohydrates are what we use to fuel for a workout because they are easily for your body to quickly absorb. But when your workout is done, focus on complex carbohydrates that come from whole foods.
Complex carbohydrate examples would be things like sprouted bread, brown rice, quinoa, yams, potatoes, and fruits. Getting as close to the whole food as possible will give you the most fiber, vitamins, minerals, antioxidants, and phytochemicals, and that also means better digestion and gut health. Brenda Davis reminds us, “throughout the world, people who eat unprocessed or minimally processed diets that are rich in whole food carbohydrates enjoy remarkably good health, especially in the Blue Zones where people live the longest and without lifestyle diseases." 

Myth 4: Intermittent Fasting Works for Everyone

Intermittent fasting - a popular practice that involves periods of severely reduced caloric intake or completely avoiding food for a period of up to 24 hours - can be effective in treating metabolic diseases, especially in an inactive population, and may be effective for weight loss especially for men. But what about athletes using intermittent fasting for weight and performance benefits? Dr. Stacy Sims, an expert in female physiology and nutrition, suggests that intermittent fasting can be harmful to performance and health for active women.

But what is it about intermittent fasting specifically might be not as healthy for women? Through research with females, she has narrowed down what happens to the female body in a fasted state. She says, “It comes down to kisspeptin, is a neuropeptide that’s responsible for sex hormones and endocrine and reproductive function, which also plays a significant role in maintaining healthy glucose levels, appetite regulation, and body composition. It’s also more sensitive in women than men. When it gets perturbed, our sex hormones aren’t produced and released the way we need them to be.” That translates to weight gain, rises in cortisol, and depressed thyroid activity which are the opposite of the desired effect of intermittent fasting.
Get my free sports nutrition ebook here to learn what and when to eat, and information on supplements and caffeine!
Listen to my podcast with Sports Nutritionist Anne Guzman: Nutrition Tips for Endurance Athletes

Sonya Looney is a World Champion Endurance Athlete, Health Coach, and Podcast Host of the Sonya Looney Show. She has her MS in Electrical and Biomedical Engineering and her certificate in Plant-Based Nutritional Studies from Cornell University.