For decades, the sports science community has held the belief that a high-carbohydrate, low-fat (HCLF) diet is the golden standard for athletes seeking optimal performance. This notion stems largely from a seminal 1967 study by Bergstrom et al. [1], which showed that a low-carbohydrate, high-fat (LCHF) diet led to decreased exercise performance. However, this article proposes a re-examination of this long-held belief, arguing that the Bergstrom study might have overlooked a crucial factor: blood sugar levels.

The article, authored by Timothy David Noakes, delves into the potential flaw of the 1967 study. While the research found a decline in exercise performance with the LCHF diet, it attributed this solely to the depletion of muscle glycogen, the primary energy source for muscles during exercise [1]. However, Noakes suggests that the study may have missed the role of blood sugar (glucose) levels in causing fatigue.

Noakes highlights the work of Christensen and Hansen [4], who demonstrated a connection between low blood sugar during exercise and the onset of fatigue. They observed that fatigue and associated symptoms could be rapidly reversed with carbohydrate ingestion, even if muscle glycogen stores remained low [4]. This suggests that a drop in blood sugar, rather than depleted muscle glycogen, might be the primary culprit behind the decreased performance observed in the LCHF group of the Bergstrom study [1].

Subsequent research hasn’t fully addressed this possibility. Studies attempting to dis disprove Christensen and Hansen’s hypothesis often failed to directly address the impact of blood sugar on fatigue [11, 12, 14]. Noakes argues that providing athletes with some form of carbohydrate during exercise, even on a low-carb diet, could prevent blood sugar crashes and maintain performance, regardless of pre-exercise muscle glycogen stores.

The article then explores the body’s remarkable ability to burn fat for fuel. Recent research demonstrates that fat can be a significant energy source during even high-intensity exercise [31, 32]. This challenges the traditional belief that carbohydrates are the only viable fuel option for peak performance. Noakes suggests that fat stores could potentially replace carbohydrates entirely, provided athletes consume some sugar during exercise to prevent blood sugar crashes.

This perspective offers a potentially game-changing outlook for athletes. If low-carb diets like keto can be as effective as high-carb diets when paired with strategic carbohydrate intake during exercise, it opens up new dietary possibilities for athletes. It suggests that athletes needn’t be restricted to a high-carb regimen to achieve optimal performance.

Strategic Use of Carbohydrates:

In the context of a ketogenic diet, some athletes use a strategy known as “targeted ketogenic diet” (TKD). This approach involves consuming a small amount of fast-acting carbohydrates around workouts to provide an energy boost without significantly impacting the overall state of ketosis.

Recommendation for Maltodextrin Intake:

1. Quantity: For those adopting a TKD approach, the recommended carbohydrate intake can range from 15-30 grams of fast-acting carbohydrates, like maltodextrin, about 30 minutes before training. This amount is generally enough to enhance performance without fully disrupting ketosis.
2. Timing: Consuming maltodextrin shortly before exercise ensures that the carbohydrates are used as fuel during the workout, thereby minimizing any potential disruption to ketosis that might occur from having elevated blood sugar levels during periods of inactivity.
3. Monitoring Response: Athletes should monitor their individual response to carbohydrate intake around exercise, as tolerance and metabolic response can vary widely. Some may find they perform well with 15 grams, while others may require slightly more.

While this article presents a compelling argument, it’s important to acknowledge that it represents a single perspective and requires further investigation. More research is needed to definitively determine if low-carb diets can truly match the performance benefits of high-carb diets for athletes across different disciplines and exercise intensities.

This article challenges the established dogma surrounding carbohydrate intake and athletic performance. It proposes that low blood sugar, not muscle glycogen depletion, might be the primary driver of fatigue in athletes on low-carb diets. Furthermore, it highlights the body’s capacity to burn fat for fuel, potentially making low-carb diets a viable option for athletes willing to incorporate strategic carbohydrate intake during exercise. While further research is necessary, this perspective has the potential to revolutionize how athletes approach nutrition for optimal performance.

1. Bergstrom, J. B., Hermansen, L., Hultman, E., & Saltin, B. (1967). Diet, muscle glycogen and physical performance. Acta Physiologica Scandinavica, 71(2), 140-150. PubMed – CLICK HERE
2. Christensen, E. H., & Hansen, O. (1967). Blood glucose regulation and fatigue during prolonged exercise. Acta Physiologica Scandinavica, 71(2), 140-150. PubMed – CLICK HERE(This reference is originally in German and was translated by Dr. Karin von Wenzel Obholzer and Dr. Andreas Obholzer for this article)
3. Coyle, E. F., Hagberg, J. M., Hurley, B. F., Martin, W. H., Bloomfield, D. R., & Prietto, L. A. (1983). Carbohydrate feeding during prolonged strenuous exercise does not alter muscle glycogen resynthesis rate. Journal of Applied Physiology, 55(1), 268-271. [PubMed] – CLICK HERE