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Case Study: Higher-Carb Fueling to Improve Performance

When this pro athlete stopped restricting nutrition and fueling in favor of a higher-carbohydrate diet, she was surprised by the result.

Woman pours freshly-squeezed juice into a glass

Nutritionist Scott Tindal was able to help one of his pro triathlete clients come to the realization that she may have been underfueling for much of her career. She had been in a caloric deficit for quite a while, after a foot injury forced her do her run training on an anti-gravity treadmill. Because running at ten pounds lighter felt so much better, she decided to target that weight and see if her performance improved.  

Tindal first asked the athlete to get a DEXA scan to measure bone density and body composition, explaining, “We should listen to athletes because they often know the answer to a lot of things that they are going through.” He wanted to quantify whether there was a reason for her to reduce her weight. In fact, the DEXA scan indicated that she was quite lean.  

Fortunately, the fact that she had been underfueling didn’t impact her bone mineral density. When athletes are well under their fueling targets for a prolonged period of time, they will enter a state of low energy availability (LEA), which can, over time, cause a loss of bone mineral density. “There’s a high proportion of triathletes and cyclists who have low mineral density,” said Tindal. “She was fortunate that her health was not impacted.”  

Blood testing revealed that the athlete had low ferritin levels (stored iron), so as they worked on a new strategy for her nutrition and fueling, she began to follow the Fuelin nutrition program. The Fuelin app syncs with the athlete’s training platform (in this case, TrainingPeaks), to provide a personalized nutrition and fueling plan. The program emphasizes fueling for the work required. This means that each workout and meal is mapped out based on the training completed.  

Education on nutrition science is a big part of the program. One area that was adjusted was the athlete’s protein intake. Tindal adds that every athlete, pro or amateur, young or old, benefits from getting more protein. Aiming for at least 2 grams of protein per kilogram of body weight is a good start. With the assistance of blood testing, the pro benefitted from a targeted nutrition plan and a selection of supplements, such as iron, vitamin D, and omega 3s, to help remedy the specific issues identified. 

Increasing carbohydrates to improve performance 

The triathlete said that her underfueling was most noticeable to her after bigger days of training. She typically ate more on recovery days despite not training as hard. When she increased her fueling to match the demands of her training, not only did she experience less hunger and cravings on her recovery days, she also found it easier to get the harder sessions done. 

Tindal stresses that all athletes can benefit from refining their strategy and consistently practicing it in training: “You don’t have to be a pro athlete, you just have to recognize what your body needs.”   

Now, the pro follows a higher-carbohydrate fueling protocol two to three times a week in her high-intensity sessions, which typically consist of a ride followed by a run session. It no longer feels like practicing her race nutrition, just part of training and recovery.  

RELATED: High Carbs for Big Adventures  

In preparation for a key race, she targets at least 8 grams of carbs per kilogram of body weight in the 24 hours leading up to a race. During the race, she is averaging over 100 grams per hour on the bike and over 70 grams per hour on the run. Some athletes have a more difficult time reaching comparable targets as they manage gut issues or sensitivity.  

Fuelin offers athletes a tool to test and improve their carbohydrate capacity in training and racing. One of the ways to improve GI distress during racing is to practice higher-carb fueling during training. This concept is known as “training the gut.” It is one of the ways that Fuelin helps athletes improve their race performance. 

Everything is back on the table 

Working with Fuelin led the triathlete to reintroduce foods to her diet that she had long avoided. She transitioned from a gluten-free diet to eating more carbohydrates, particularly around her high-intensity training. Over time, eating became more enjoyable because she was able to put her fear of gaining weight behind her.  

Eating outside of training also became easier for her when she started viewing her fueling separately from her daily nutrition. Previously, she would be thinking about restricting her diet if she had fueled more for a hard session, whereas now she focuses on the macronutrient targets for her daily nutrition as a separate goal, no different from executing her training plan.  

Tindal stresses that higher-carbohydrate diets include plenty of vegetables and leafy greens. Pros are eating 6 or 7 servings of vegetables every day. On lower-carbohydrate days, or “red” days in the Fuelin app, grains and root vegetables are less prevalent. Fat intake can be increased on these days to maintain an adequate caloric intake if required.  

Example of red/yellow/green nutrition guidelines from Fuelin

The prescription for lower-carbohydrate days will vary depending on the athlete and their body mass. In this pro’s case, a lower-carbohydrate day would be between 150–200 grams, which is equivalent to 2.5 to 3.3 grams of carbohydrate per kilogram of body weight. Lower-carb days do not mean no carbs. Consumption is relative to the work being performed.

While there is a growing interest in lower-carbohydrate diets, research has shown it can be detrimental to the ability to utilize carbohydrates in high-intensity, high-volume training and racing. Very low carbohydrate diets or keto diets will restrict carbs to less than 50 grams per day, which is not in agreement with the Fuelin philosophy. 

In the pro ranks, athletes are pushing for higher targets and seeing performance improve. Research indicates that fueling and eating adequate carbohydrates also benefits sleep, mood, and recovery. ​​​The importance of carbohydrates for bone health is also established through research. Restricting carbohydrates, especially following exercise, can prove detrimental to bone structure in both acute and chronic timeframes. ​  

Dialing nutrition and fueling can bring about significant improvements to performance, particularly if athletes and coaches are willing to gather the data and consistently execute the plan. Most athletes experience the biggest gains season over season, both in terms of sport performance and their overall health and well-being.