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The Effect of a Low-Carbohydrate Diet on Performance, Hormonal and Metabolic Responses to a 30-s Bout of Supramaximal Exercise

Langfort, J., Zarzeczny, R., Pilis, W., et al., "The Effect of a Low-Carbohydrate Diet on Performance, Hormonal and Metabolic Responses to a 30-s Bout of Supramaximal Exercise," European Journal of Applied Physiology, 76(2), 1997, pages 128-133.

In this study, researchers examined whether a low-carbohydrate diet affects the capacity for all-out anaerobic exercise as well as the hormonal and metabolic response to this type of exercise. Eight healthy subjects were divided into two groups. Group 1 adhered to a mixed diet (31 calories per kilogram of body mass: 50% carbohydrate, 30% fat, 20% protein) for three days. Group 2 followed a low-carbohydrate diet of the same caloric value (31 calories per kilogram of body mass: 5% carbohydrate, 50% fat, 45% protein) for 3 days. Subjects then took the Wingate bicycle test, pedaling all out for 30 seconds. Before and in the one-hour time frame after the test, venous blood samples were collected and analyzed for lactate, beta-hydroxybutyrate (a particular ketone body), glucose, adrenaline, noradrenaline, insulin and oxygen. After consuming a low-carbohydrate diet, subjects in Group 2 had higher concentrations of beta-hydroxbutyrate and noradrenaline, while glucose and insulin were lower, compared to subjects in Group 1. Three minutes after the exercise test blood lactic acid levels were also lower and one hour after, adrenaline and noradrenaline were higher. Blood beta-hydroxybutyrate concentration decreased quickly after exercise (30% of pre-exercise value within 60 minutes). The researchers concluded that a low-carbohydrate diet is detrimental to anaerobic work capacity, possibly because of reduced stores of glycogen in the muscles and decreased rate of glycolysis; but there is enhanced activity of the sympathoadrenal (“fight or flight” system) at rest and after exercise.

The following information was written by Atkins professionals.

The findings from this study can be applied to the Atkins Principle of Good Health. Carbohydrate controlled nutrition may improve athletic performance. Three minutes after an all-out bicycle test, lactic acid levels were lower in individuals on the low-carbohydrate diet compared to those on the mixed diet. Lactic acid has been implicated in the burning sensation within the muscle caused by certain exercises. Lower lactic acid levels can be equated to quicker recovery time. Thus the muscle will be able to begin a second bout of exercise much sooner. Increased beta-hydroxybutyrate (a specific type of ketone body) at rest was an indication that fat was the major energy source being used. Increased levels of adrenaline and noradrenaline, as a result of enhanced activity of the sympathoadrenal system, are also beneficial in terms of body fat loss. These two hormones “turn on” the process of lipolysis (fat breakdown). Elevated levels may equate to increased lipolysis. The researchers’ conclusion that a low-carbohydrate diet was detrimental to anaerobic work capacity may have been premature. Subjects on the low-carbohydrate diet for three days were still in the process of transitioning to a fat-burning metabolism. The body may not have been fully adept yet at using fat for energy, thus causing a poorer anaerobic performance.