How do popular dietary trends impact athletic performance?

By Dr. Priyom Bose, Ph.D.Aug 29 2023Reviewed by Sophia Coveney

For the optimum performance of athletes, nutrition is of utmost importance. Research has led to the development of numerous diet patterns and many of these have also been endorsed by professional athletes. A recent Nutrients study critically evaluated the existing research on diets and their impacts on athletic performance.

Background

Nutrition is key for the optimum performance and recovery of athletes. The American College of Sports Medicine, American Dietetic Association, and Dietitians of Canada recommend combinations of foods and fluids that supply athletes with ample nourishment and energy to maintain their high-intensity training and recovery.

Athletes of all levels, from youth to professional, are being exposed to an array of diet patterns and nutrition through social media, peers, and coaches. The most frequently researched diets include the Mediterranean diet (MedDiet), low-carbohydrate and ketogenic diets, intermittent fasting, and vegetarian and plant-based diets. 

About the study

The current study critically analyzed the current literature on the above-mentioned diets. More specifically, it described the content of the diet, feasibility for adherence, potential drawbacks, and impact on sports performance.

It must be noted that the current study focussed on the five most common dietary patterns studied in the literature from the PubMed search and does not comprehensively discuss all diets and their impacts on athletic performance.

Narrative and systematic reviews and meta-analyses from 2015–2022 were first considered. Subsequently, the primary literature cited within these works was also studied.

Key findings

The MedDiet has been recommended from a performance and body composition standpoint. It has a low inflammatory index and provides the required nutritional support. The MedDiet supports training and performance gains while promoting weight loss if required.

Athletes adhering to the MedDiet have observed gains in aerobic and anaerobic performance, which suggests that it is beneficial for power and endurance athletes. Owing to the improvement in body composition, athletes can sustain performance during long training or competitions. Given the wide range of foods within the MedDiet, adherence is relatively easier compared to other diets.

A ketogenic diet (KD) is high In fat, very low in carbohydrates, and moderate in protein. Existing literature suggests that KD has little impact on maximum aerobic capacity. It must be noted that athletes adhering to KD may experience performance decrements in strength training because they do not meet daily caloric needs and may have reduced muscle mass.

KD has also been seen to impact bone health in endurance athletes negatively. During intense training periods and especially for endurance athletes, it is generally advised to avoid chronic carbohydrate restriction. Also, given the strict carbohydrate percentage cut-offs, adherence to KD is quite difficult.

An alternative to the KD is the non-ketogenic low-carbohydrate diets, which include KD but are more liberal on carbohydrate intake. Overall, such low-carbohydrate diets have not shown any changes in athletic performance.

It must, however, be flagged that they promote adherence, given fewer restrictions. Similar to KD, future research should explore more sport-specific alterations to performance.

Vegetarian diets range from veganism, which is not eating any type of animal or animal by-products, to vegetarianism, which is not eating any animal flesh but consuming eggs and dairy.

There are many benefits in adopting such diets; however, athletes could develop micronutrient deficiencies. In the existing literature, the size of these deficiencies and their impact on performance are unclear.

Intermittent fasting (IF) involves restricted eating at certain hours of the day or fasting for a full day or multiple days at a time. Overall, the risks of IF may outweigh its benefits among athletes. Meeting the caloric intake for muscle mass maintenance and training performance is already difficult for athletes.

It becomes more complicated when the eating window is reduced. The overall results are varied, which requires more research on the impact of IF on performance.

Conclusion

Overall, the MedDiet was seen to have the most extensive research on improvements in performance and diet adherence. It provides adequate nutrition to help athletes recover and continue training.

Low-carbohydrate diets and ketogenic diets may be conflated by many. The former has shown more adherence, but neither has been shown to be detrimental to athletic performance.

Vegans and vegetarians could suffer from micronutrient deficiencies, such as vitamins and minerals, and such diets may have lower leucine content. Plant-based athletes should have higher protein intake compared to omnivore athletes.

In existing research, individuals on plant-based diets have not been seen to report inferior performance. Lastly, IF has been shown to reduce athletic performance levels in both endurance and aerobic sports performance.