Initially, you may experience a rapid drop in weight. After a period of time, your weight may plateau and possibly even increase. The phenomenon is partly due to the composition of glycogen, which is primarily water. In fact, the water in these molecules accounts for three to four times the weight of the glucose itself. As such, rapid depletion of glycogen at the onset of the diet triggers the loss of water weight. Over time, glycogen stores are renewed and the water weight begins to return.
When this happens, weight loss may stall or plateau. Gains experienced in the beginning come from water loss, not fat loss, and are only temporary. Fat loss can continue despite the short-term plateau effect. The body can store around 2, calories of glucose as glycogen. For endurance athletes who burn that many calories in a couple of hours, the amount of stored glucose can be an impediment.
When these athletes run out of glycogen, their performance almost immediately begins to suffer—a state commonly described as "hitting the wall.
If you're undertaking a strenuous exercise routine, there are several strategies endurance athletes use to avoid decreased performance you may find helpful:. Get exercise tips to make your workouts less work and more fun.
Low-carbohydrate weight-loss diets. Effects on cognition and mood. Glycogen metabolism in humans. BBA Clinical. The effects of a ketogenic diet on exercise metabolism and physical performance in off-road cyclists. Your Privacy Rights. To change or withdraw your consent choices for VerywellFit. At any time, you can update your settings through the "EU Privacy" link at the bottom of any page. These choices will be signaled globally to our partners and will not affect browsing data. We and our partners process data to: Actively scan device characteristics for identification.
While glycogen is indispensable to athletes, we have a very limited capacity to store it. Despite its limited storage capacity, glycogen is crucial for energy production at all levels of effort. Research has shown that aerobic endurance is directly related to the initial muscle glycogen stores, that strenuous exercise cannot be maintained once these stores are depleted, and that perception of fatigue during prolonged intense exercise parallels the decline in muscle glycogen 3.
Ensure you are optimizing glycogen stores before exercise, maintaining it during exercise, and replenishing it after exercise. What is Glycogen? Immediately after physical activity, muscle cells that sustained a substantial decrease in glycogen content are metabolically prepared for rapid glycogenesis. In brief, glycogen use during exercise turns on glycogen synthesis during recovery.
When carbohydrates are ingested soon after exercise, insulin release from the pancreas, insulin sensitivity in muscle cells, glucose uptake by muscle cells, and glycogen synthase activity within muscle cells all increase, 94 responses that can remain elevated for 48 hours.
As noted above, timing of carbohydrate intake following physical activity is very important during training and competition requiring multiple efforts during a single day. Daily carbohydrate intake should reflect the extent of carbohydrate oxidation during training: low on light training days, substantially higher on days of intense or prolonged training. Table 3 contains related practical recommendations.
Recommendations for daily carbohydrate intake for athletes involved in repeated days of strenuous, prolonged physical activity and training. Adapted from Thomas et al. In their review of the literature, Burke et al. It is true that fructose better stimulates liver glycogen restoration and glucose does the same for muscle glycogen, but most physically active people normally ingest enough fructose and glucose in foods and beverages to restore liver glycogen. Consequently, there is no need to be concerned with the adequacy of dietary fructose intake.
It should be noted that combinations of glucose, fructose, and sucrose consumed in sports drinks during exercise have been shown to enhance the rate of fluid absorption from the proximal small intestine and improve the rate of carbohydrate oxidation during exercise, , 2 important factors in sustaining exercise performance. Solid and liquid forms of carbohydrates are associated with similar rates of glycogen synthesis, — so athletes can meet their daily carbohydrate needs by consuming the carbohydrate-rich foods and beverages they most enjoy.
Interestingly, Cramer et al. In the hours soon after exercise, consuming high—glycemic index GI foods can speed muscle glycogen restoration. Low-GI foods are digested and absorbed more slowly than high-GI foods, differences that result in a slower rise in blood glucose and insulin levels, an effect that can last for hours after eating.
The meals were consumed 2 hours prior to exercise. Compared with a placebo treatment no meal , both the low- and high-GI meals improved the total run distance during sprints conducted in the last 15 minutes of the minute session. In contrast with no pre-exercise meal, muscle glycogen levels prior to the final minute segment of exercise were similarly higher with both low- and high-GI meals. The authors attributed improved run performance to higher muscle and possibly liver glycogen levels prior to the final sprints.
Consuming high-GI carbohydrates is effective in increasing muscle glycogen stores after exercise. Increasing the carbohydrate content of the diet to However, Brown et al. As is often the case in science, additional research is needed to further clarify the conditions in which consuming high-GI foods benefits glycogen restoration and performance. Waxy starches from varietals of potatoes, corn maize , and barley are high in amylopectin and low in amylose; amylopectin is less resistant to digestion because its glucose chains are more highly branched compared with amylose.
For that reason, waxy starches have been studied to assess how their ingestion influences glycogen metabolism and exercise performance. Postexercise muscle glycogen concentrations were similar among treatments, but 24 hours later, less glycogen had been replenished with resistant starch compared with the other treatments.
Total glycogen repletion with glucose was greater than that with waxy starch was greater than that with maltodextrin was greater than that with resistant starch. A companion study by Goodpastor et al. Additional research on the metabolic and performance responses to the ingestion of waxy starches is warranted simply because of the dearth of research in this area. In terms of overall health, high-quality carbohydrates from unprocessed or minimally processed whole grains, vegetables, beans, dairy foods, and fruits also provide numerous vitamins, minerals, fiber, and many important phytonutrients.
Increased consumption of high-quality carbohydrate foods, such as potatoes and grains, can help ensure adequate consumption of nutrients vital to health, recovery, repair, adaptation, growth, and performance. Aside from the purposeful manipulation of muscle glycogen concentration by diet and training nutrition periodization , periods of extended fasting during Ramadan or in attempts to lose body weight result in metabolic responses that are usually contrary to maintaining high muscle glycogen concentrations, especially if training continues during the fasted state.
Prolonged fasting and very low—carbohydrate diets result in ketosis ketoacidosis , sparing liver and muscle glycogen. As a result, ketotic diets and the ingestion of ketone bodies have been suggested as possible ergogenic aids, particularly for endurance and ultra-endurance athletes.
Related to that conclusion, Vandoorne et al. In short, more research is needed to further clarify the metabolic and performance responses to ketosis—whether induced by fasting, prolonged low-carbohydrate diets, or by the ingestion of ketone bodies—across performance parameters, with special reference to the mental and physical responses during ultra-endurance events when fat oxidation normally predominates.
This relatively slow time course makes it impossible for those engaged in multiple bouts of intense exercise during a single day to fully restore muscle glycogen between training sessions or competitive efforts. However, it is possible to maximize the rate of short-term muscle glycogen repletion so that athletes can replenish more muscle glycogen than might otherwise be possible. Consuming proteins with carbohydrates may be beneficial in stimulating rapid glycogenesis in the hours immediately following exercise, 65 a finding that has implications for speeding recovery between demanding bouts of exercise within the same day.
A greater glycogen storage rate may be due to increased muscle glucose uptake and enhanced signaling pathways made possible by the influx of amino acids. Protein consumption also induces a rise in blood insulin concentration that augments the insulinemic response to carbohydrate ingestion, increasing the rate of glycogen repletion.
Consumption of 0. It is clear that adequate consumption of proteins stimulates muscle protein synthesis during rest, although consuming proteins during exercise does not appear to benefit performance or immune function or reduce muscle damage. Multiday supplementation with creatine monohydrate along with an adequate amount of carbohydrates has been reported to increase muscle glycogen synthesis compared with carbohydrate ingestion alone.
Males and females appear to restore muscle glycogen at similar rates following exercise, as long as sufficient carbohydrates and energy are consumed. The additional protein intake might also help facilitate glycogen synthesis, especially when carbohydrate intake is low.
The Dietary Guidelines for Americans identifies gap nutrients as dietary fiber, choline, potassium, magnesium, calcium, and vitamins A, D, E, and C. Data are from the US Department of Agriculture. Nutrient-rich foods that are high in carbohydrates include grains cereal, rice, pasta, breads, etc , most fruits, some vegetables especially starch vegetables such as potatoes, beans, and peas , and dairy foods.
Fruit and dairy foods contain simple sugars yet are rich in key nutrients. Fruit, especially whole fruit, is a good source of dietary fiber, vitamins, minerals, and water.
Dairy foods, such as milk, are a good source of calcium, vitamin D, and potassium. The nutrition facts panel on packaged food can steer athletes to high-quality carbohydrate foods. The nutrition facts panel contains 2 pieces of information that athletes can readily use to identify carbohydrate content: the serving size and the grams of carbohydrates per serving.
For example, 1. Currently, the nutrition facts panel does not distinguish naturally occurring sugar from added sugar, but proposed changes to the nutrition label will eventually separate the 2 sugars on product labels. This is important because the current nutrition label identifies milk as containing 12 grams of sugar per cup, but this sugar is the naturally occurring milk sugar, lactose, not sugar added in processing.
Identifying portion sizes can be a challenge for many athletes. Frequently, portion sizes are identified in ounces or grams or common household measures, such as cups, but many athletes are unfamiliar with the translation of those units to what constitutes a single serving. Using common household objects as a benchmark can help athletes understand serving sizes.
A useful guide can be found at Web MD, and athletes can use these tools to help them easily visualize a serving. As identified in Table 3 , athletes who exercise very hard every day or perform very prolonged exercise have a high requirement for dietary carbohydrates. There are also many high-carbohydrate drinks, gels, bars, and shakes that can be consumed to boost carbohydrate intake.
Athletes should pack snacks to consume between training sessions and not rely on coaches or the venue to provide quality snacks. Several sports foods carbohydrate chews, bars, gels are available in a variety of flavors and can be convenient for athletes. However, athletes are advised to try sports foods during training to know which foods they tolerate and enjoy.
A high-carbohydrate diet remains the evidence-based recommendation for athletes who engage in hours of physical activity on a daily basis. To maintain muscle glycogen stores, athletes are advised to consume a high-carbohydrate diet that contains adequate energy calories , along with proteins to stimulate muscle repair and growth and fluids to ensure normal hydration. Glycogen supercompensation results from a combination of ample rest, reduced training volume, and the consumption of a high-carbohydrate diet.
Consumption of a variety of carbohydrate foods ensures adequate muscle and liver glycogen restoration between bouts of physical activity. High-quality, nutrient-rich carbohydrates, such as potatoes, pastas, breads, vegetables, and fruits, provide concentrated amounts of simple mono- and disaccharides, maltodextrins and complex starches and fibers carbohydrates along with an array of micronutrients, such as vitamins, minerals, and other nutrient compounds.
To allow for sufficient muscle glycogen restoration between training sessions and overnight, athletes should consume enough carbohydrates to replace all or at least a substantial amount of the glucose oxidized during the day.
Glucose oxidation can vary widely from day to day, so carbohydrate and energy intake should also vary—higher on days of hard training, lower on days of easier training. After hard exercise, nutritious, carbohydrate-rich foods such as potatoes, pastas, grains, vegetables, and fruits are important sources of carbohydrates that can be quickly digested, absorbed, and transported in the blood and taken up by muscles and liver for the restoration of glycogen stores.
When rapid glycogen resynthesis is required, consuming 0. When 24 hours or more are available for glycogen restoration, the frequency of carbohydrate intake is less important than the total amounts of carbohydrates and energy consumed.
Techniques such as training with high muscle glycogen stores but sleeping and then training the next morning with low muscle glycogen stores have been shown in some studies to enhance glycogen storage and performance. However, more research is needed to confirm the consistency and magnitude of these responses.
For anyone engaged in regular physical activity eg, laborers and soldiers or sports training, adequate restoration of muscle and liver glycogen stores from day to day is required to sustain the capacity for continued exercise and high-intensity activity.
If glycogen stores in muscle reach a critically low level, exercise intensity markedly decreases and performance is impaired. If liver glycogen stores are compromised, blood glucose declines, creating a hypoglycemic state that impairs both physical and mental function.
Consumption of a variety of foods containing carbohydrates is needed to replenish all or a substantial portion of the glycogen that is oxidized during physical activity.
Athletes, laborers, and soldiers are well advised to consume diets containing a variety of foods rich in carbohydrates and other nutrients and to begin consuming such foods as soon as possible following glycogen-depleting exercise or activity.
National Center for Biotechnology Information , U. Nutr Rev. Published online Feb Bob Murray 1 and Christine Rosenbloom 2. Author information Copyright and License information Disclaimer. E-mail: moc. For commercial re-use, please contactjournals. This article has been cited by other articles in PMC. Abstract The ability of athletes to train day after day depends in large part on adequate restoration of muscle glycogen stores, a process that requires the consumption of sufficient dietary carbohydrates and ample time.
Keywords: dietary carbohydrates, exercise recovery, muscle glycogen, sports nutrition. Tissue Average g Normal range g Muscle — Liver 80 0— Open in a separate window.
Figure 1. Figure 2. Table 2 Dietary and exercise interventions that influence muscle glycogen synthesis. No clear evidence of additional benefits to glycogen stores or performance Bartlett et al. Performance benefits could be due to higher muscle glycogen Hawley 60 ; Marquet et al. However, fat loading can impair muscle CHO oxidation and performance at higher intensities Bartlett et al.
Figure 3. Figure 4. Table 4 High-quality carbohydrate foods. Achieving a high-carbohydrate diet As identified in Table 3 , athletes who exercise very hard every day or perform very prolonged exercise have a high requirement for dietary carbohydrates. Acknowledgments Author contributions. Declaration of interest. References 1. Carbohydrate dependence during prolonged, intense endurance exercise.
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