Despite the common misconception that meat gives us energy, hard-working muscles run primarily on glycogen, a form of carbohydrate stored in our liver and muscle. Carbohydrates, which come almost exclusively from plants, also provide our brain with its primary and preferred fuel — glucose — which helps us stay sharp and focused during intense training sessions, competitions (1), or long days at work or at home (2).
Performance-based diets built around meat and other animal products often provide dietary fat at the expense of carbohydrates (3-6). Unlike carbohydrates, fat can’t produce energy fast enough to meet the demands of intense exercise, so diets that sacrifice carbohydrates typically impair high-intensity performance (1). Low-carbohydrate diets, including the ketogenic (keto) diet, have been shown to cause so much fatigue that they even affect our motivation to begin a training session, let alone finish it (7-9).
Protein can also be used as a fuel source, but it’s highly inefficient, wasting 20-30% of each calorie as heat (10).
All told, carbohydrates are the ideal source of energy for optimized performance, whether it’s doing squats, playing football, or running a marathon.
And as we discuss in Getting and Staying Lean, despite the common misconception that “carbs make you fat”, unrefined carbohydrates — like those found in whole plant foods, including oats, sweet potatoes, and bananas — are consistently associated with decreased body fat, another advantage for most performance and fitness goals.
References:
(1) Thomas DT, Erdman KA, Burke LM. American College of Sports Medicine Joint Position Statement. Nutrition and Athletic Performance. Med Sci Sports Exerc. 2016 Mar;48(3):543-68.
(2) Berg JM, Tymoczko JL, Stryer L. Biochemistry. 5th edition. New York: W H Freeman; 2002.
(3) Kanter M. High-Quality Carbohydrates and Physical Performance: Expert Panel Report. Nutr Today. 2018;53(1):35-9.
(4) Masson G, Lamarche B. Many non-elite multisport endurance athletes do not meet sports nutrition recommendations for carbohydrates. Appl Physiol Nutr Metab. 2016 Jul;41(7):728-34.
(5) Clark M, Reed DB, Crouse SF, Armstrong RB. Pre- and post-season dietary intake, body composition, and performance indices of NCAA division I female soccer players. Int J Sport Nutr Exerc Metab. 2003 Sep;13(3):303-19.
(6) Jenner SL, Buckley GL, Belski R, Devlin BL, Forsyth AK. Dietary Intakes of Professional and Semi-Professional Team Sport Athletes Do Not Meet Sport Nutrition Recommendations — A Systematic Literature Review. Nutrients. 2019 May;11(5):1160.
(7) Butki BD, Baumstark J, Driver S. Effects of a carbohydrate-restricted diet on affective responses to acute exercise among physically active participants. Percept Mot Skills. 2003 Apr;96(2):607-15.
(8) Keith RE, O’Keeffe KA, Blessing DL, Wilson GD. Alterations in dietary carbohydrate, protein, and fat intake and mood state in trained female cyclists. Med Sci Sports Exerc. 1991 Feb;23(2):212-6.
(9) White AM, Johnston CS, Swan PD, Tjonn SL, Sears B. Blood ketones are directly related to fatigue and perceived effort during exercise in overweight adults adhering to low-carbohydrate diets for weight loss: a pilot study. J Am Diet Assoc. 2007 Oct;107(10):1792-6.
(10) Westerterp KR. Diet induced thermogenesis. Nutr Metab (Lond). 2004;1(1):5.