Layne Norton Breaks Down Which Diet Is Better for Performance: Low-Carb or Low Fat?

Both diets have pros and cons, but neither is significantly better for performance than the other.

When aiming to improve one’s performance, which is the better diet to follow: low-carb or low-fat? That was the topic of a study breakdown in a video published on powerlifter and nutritional scientist Dr. Layne Norton‘s YouTube channel on March 22, 2023.

Norton dissected a 2023 crossover study in Frontiers in Nutrition that tracked subjects’ performances running at least 20 miles per week and a sub-seven-minute mile after a month on a low-carb or low-fat diet. The study sought to assess the effects on “performance, body composition, substrate oxidation, cardiometabolic, and 31-day minute-by-minute glucose (CGM) biomarkers. (1)

The same subjects followed each diet for one month before being tested for the above biomarkers. There was a “washout period” between those months. Check out the video below, wherein Norton breaks down the study’s findings:

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Low-Fat vs. Low-Carb

Although the macro breakdown for each diet was obviously different, the study was “isocaloric,” meaning that subjects consumed equal calories while following each diet. Per Norton, the study found “no difference in performance or body composition…between the groups.”

These results did not surprise Norton. As calories were consistent across both diets, body composition remaining consistent as well was more or less the expectation. Aside from “extreme exercise,” Norton also seemed unsurprised by the lack of improved performance when following one diet versus the other.

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Norton’s takeaway is that either low-carb or low-fat diets are unlikely to hinder one’s performance. His only caveat is that for pro athletes or athletes doing intense anaerobic exercise, some examples of which might be CrossFit or HYROX, a higher-carb diet might be preferential to low-carb.
However, for “most people,” Norton suggests people follow whatever diet they are comfortable staying consistent with and that supports their lifestyle.

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Editor’s Note: The content on BarBend is meant to be informative in nature, but it should not be taken as medical advice. When starting a new training regimen and/or diet, it is always a good idea to consult with a trusted medical professional. We are not a medical resource. The opinions and articles on this site are not intended for use as diagnosis, prevention, and/or treatment of health problems. They are not substitutes for consulting a qualified medical professional.


  1. Prins, P. J., Noakes, T. D., Buga, A., D’Agostino, D. P., Volek, J. S., Buxton, J. D., Heckman, K., Jones, D. W., Tobias, N. E., Grose, H. M., Jenkins, A. K., Jancay, K. T., & Koutnik, A. P. (2023). Low and high carbohydrate isocaloric diets on performance, fat oxidation, glucose and cardiometabolic health in middle age males. Frontiers in nutrition10, 1084021.

Featured image: @biolayne on Instagram