Study Reveals Impact of Low and High Glycemic Index Diets on Endurance Performance

by Ella

Endurance athletes often seek dietary strategies to optimize their performance, with carbohydrates playing a crucial role in sustaining energy levels during prolonged exercise sessions. A recent study conducted by researchers at the University of [University Name] sheds light on the effects of low and high glycemic index (GI) diets compared to a low-carb, high-fat (LCHF) diet on endurance performance.


Carbohydrates are essential for maintaining performance during extended periods of endurance exercise, as they serve as the primary fuel source for muscles. Optimal metabolic flexibility and glycogen stores are vital for achieving peak endurance performance. However, the type and timing of carbohydrate consumption can significantly impact athletic performance.


Previous research has shown that LCHF diets may enhance fat oxidation but can lead to reduced glycogen stores and impaired carbohydrate metabolism, ultimately limiting performance at high intensities. Conversely, high-carbohydrate diets with low GI have been proposed as an alternative approach to improve metabolic flexibility and performance outcomes.


About the Study:

The 10-week interventional study aimed to compare the effects of three different diets: LCHF, high-GI carbohydrate-rich diet (HIGH-GI), and low-GI carbohydrate-rich diet (LOW-GI) on various metabolic parameters and endurance performance measures.


The study evaluated muscle energy stores, running economy, peak running speed, and peak oxygen consumption through a series of assessments, including a five-kilometer time trial and graded exercise test.


Study Findings:

The LOW-GI diet resulted in reduced energy intake, decreased blood lactate concentrations during exercise, higher values in the graded exercise test, maintenance of glycogen stores, and improved time trial performance.

While the LCHF diet enhanced fat oxidation, it also altered carbohydrate oxidation and muscle glycogen restoration, negatively impacting performance at higher intensities.

The HIGH-GI diet improved performance at high intensities and increased muscle glycogen content but led to impaired fat oxidation after 10 weeks.


The study findings suggest that compared to LCHF or HIGH-GI diets, the LOW-GI diet may lead to beneficial changes in substrate oxidation during prolonged exercise and improve endurance performance.

However, researchers caution against the long-term health implications of the LCHF diet, highlighting the importance of balanced macronutrient intake for overall well-being.

Limitations and Future Directions:

Limitations of the study include self-reported dietary monitoring and the need for further research to account for different sexes and explore alternative macronutrient intake strategies.

Future studies incorporating metabolomics analyses could provide insights into the underlying mechanisms associated with the observed benefits of different dietary approaches on endurance performance.

In conclusion, the study underscores the significance of dietary choices in optimizing endurance performance and highlights the potential benefits of low GI carbohydrate-rich diets in sustaining energy levels during prolonged exercise.



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