A Low-carb Diet Reduced Total Work Capacity

Nutritional strategies need to be specific to individual goals. With evidence that they may decrease the risk of diabetes, decrease heart disease, and improve weight loss, low-carb diets prove popular

On the other hand, research shows that high-carbohydrate diets improve performance in both prolonged and low-to-moderate intensity as well as short, high-intensity exercises.^1-3 What are the pros and cons of these seemingly opposite nutritional strategies?

Academic nutritionists from Poland shed some light on this subject.⁴ They conducted several measurements of basketball players consuming a conventional diet. Then researchers fed the athletes a low-carb diet for four weeks, took more measurements, fed them a carb-loading diet for seven days, and took a third set of measurements. Here’s what they found:

The low-carbohydrate diet significantly decreased resting values of pH and blood lactate concentration.
After the low-carbohydrate diet, testosterone and growth hormone concentrations increased, while the level of insulin decreased.
After a week of carb-loading, resting values of pH, bicarbonate, and lactate increased significantly compared with the results obtained after the low-carbohydrate diet.
Four weeks of the low-carbohydrate diet decreased total work capacity, which returned to baseline values after the carbohydrate loading procedure.
Neither low-carbohydrate feeding nor carbohydrate loading affected peak power.

The researchers discuss possible strategies for athletes alternating low- and high-carb diets at different phases of training and competition. The low-carb diet seems to bring changes that theoretically should enhance strength training, such as improved levels of testosterone and growth hormone. On the other hand, maintaining a low-carb diet up until endurance competition or while work capacity feels diminished in daily life may bring disadvantages in terms of work capacity.

References

Hargreaves, M. Exercise, muscle, and CHO metabolism. Scand. J. Med. Sci. Sports 2015, 25 (Suppl. 4), 29–33.
Hawley, J.A.; Burke, L.M. Carbohydrate availability and training adaptation: Effect on cell metabolism. Sport Sci. Res. 2010, 38, 152–160.
Romijn, J.A.; Coyle, E.F.; Sidossis, L.S.; Gastaldelli, A.; Horowitz, J.F.; Endert, E.; Wolfe, R.R. Regulation of endogenous fat and carbohydrate metabolism in relation to exercise intensity and duration. Am. J. Physiol. Endocrinol. Metab. 1993, 265, E380–E391.
Michalczyk MM, Chycki J, Zajac A, Maszczyk A, Zydek G, Langfort J. Anaerobic performance after a low-carbohydrate diet (LCD) followed by 7 days of carbohydrate loading in male basketball players. Nutrients. 2019 Apr 4;11(4):778.