Carbohydrate metabolism and carbohydrate loading -
Recently, use of continuous glucose monitoring CGM devices has been popularized among endurance athletes, with an aim of personalizing carbohydrate intake around exercise for optimal performance.
Certainly, knowledge of blood glucose profiles has the advantage that specific physiological data are generated from the individual athlete. These devices have a rich history in the field of diabetes treatment, and their utility has clearly been demonstrated [ ].
For a device to be deemed of use and its use recommended to a wider audience, both of the following criteria must be met: 1 the parameter that the device is measuring should have contextual relevance i.
While there is no doubt that CGM devices are useful in non-exercise contexts, their utility during exercise per se remains to be clearly established. Indeed, CGM devices appear to have limited validity during exercise [ , ], and this may be due to the complex nature of blood glucose regulation during varying types and intensities of exercise.
Blood glucose concentrations are a result of glucose uptake by the tissue and glucose appearance i. While it has been known for a long time that hypoglycemia can associate with task failure [ ], its occurrence does not always precede it [ ].
Therefore, further investigative work is required to establish whether differential blood glucose profiles using validated technology during exercise can be identified and be used to individualize carbohydrate intake during exercise. In addition to tracking glycaemia during exercise, tracking it throughout the day could also be proven useful.
A recent study utilizing CGM devices compared daily blood glucose profiles in elite trained athletes with those in a sedentary population and discovered large discrepancies in blood glucose concentrations throughout the day between both groups [ ].
Elite athletes spent more time in hyper- and hypoglycemia as compared to sedentary controls, giving an appearance that glycemic control might be impaired. While periods of hyperglycemia are expected due to post-exercise high carbohydrate intakes, observations of hypoglycemia occurring especially at night during sleep were somewhat surprising.
This knowledge can then be used to potentially individualize strategies to counter these episodes of impaired glycemic control in real time. While utilization of CGM devices during exercise to guide carbohydrate intake during exercise cannot be presently advised, athletes could individualize carbohydrate ingestion rates during exercise by establishing their highest exogenous carbohydrate oxidation rates [ 25 ].
To do this, one requires the ability to know carbon isotope enrichments of the ingested carbohydrates and in expired carbon dioxide. For example, advances have been made in methodology to easier quantify stable carbon isotope abundance in expired air [ ], a methodology currently used for quantification of exogenous carbohydrate oxidation rates [ 25 ].
Thus, this approach could be spun off from research and be used in practice as well to identify carbohydrate intake rate and carbohydrate compositions that optimize exogenous carbohydrate oxidation in individual athletes.
Finally, most research to date has investigated carbohydrate intake in a healthy male population, and thus current carbohydrate guidelines are founded on this evidence. Despite decades of intense carbohydrate research within the field of sports nutrition, new knowledge continues to be generated with the potential to inform practice.
In this article, we have highlighted recent observations that provide a more contemporary understanding of the role of carbohydrate nutrition for athletes.
For example, our article suggests a stronger emphasis be placed on scaling carbohydrate intake before competition to the demands of that subsequent activity, with particular attention paid to the effects of concomitant exercise during the preparatory period.
At high ingestion rates during exercise i. Furthermore, short-term recovery may be optimized by combining glucose-fructose to target both liver and muscle glycogen synthesis simultaneously.
Finally, there has been substantial investigation into the role of commencing selected exercise sessions with reduced carbohydrate availability to provide a beneficial stimulus for training adaptation. The abovementioned suggestions are designed to build on the wealth of knowledge and recommendations already established for athletes.
Nonetheless, what this review has also revealed is that gaps in our current understanding of carbohydrate nutrition and metabolism in relation to exercise performance remain.
Some remaining research questions arising from the present article are presented in Table 1. Answering these research questions could allow continued advancement and refinement of carbohydrate intake guidelines and, by doing that, further increase the possibility of positively impacting athletic performance.
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Athletes who compete in endurance sports, such as marathons or long-distance cycling, may thus benefit throughout their training, particularly in the heat, yet they may not want to have extra weight to carry.
For athletes that require flexibility, such as gymnastics, weight lifting, and sprinting, if muscles are packed solid with water, this may cause stiff muscles and loss in flexibility. The type of carbohydrate loading may also make a difference to saturation of glycogen.
Sports products and simple carbohydrates, such as Gatorade, PowerAde, and sports gels, are easily digested into glucose and are effective for glycogen sparing appear during an endurance event.
Carbohydrates from a complex source, such as pasta, bread, and cereal, may be more effective for training periods before an event, rather than during the event, for maximizing glycogen storage. Some early research may support the traditional technique of depletion and loading however more recent research shows that this strict routine is unnecessary.
Simply changing to a very high carbohydrate diet, combined with 1 to 2 days of rest will effectively increase muscle and liver glycogen. Furthermore, it has become evident that if an appropriate amount of carbs are consumed over the entire week rather than concentrating on the last day or two before an event, there is little glycogen difference between the 2 techniques.
Due to this particular controversy, there are obviously a number of variations of glycogen packing before an event. In summary, it is important to consider that the benefits should more than offset the extra water weight, the possibility of inflexible muscles. There was a lesser impact for patients undergoing orthopaedic and cardiac surgery Fig.
It should be borne in mind that both these meta-analyses included studies of varying quality and open to potential bias. Forest plot for carbohydrate loading vs placebo or fasting. Outcome: length of hospital stay. From Smith et al. A major area of concern for anaesthetists will centre on the safety of carbohydrate loading.
Intuitively, significant volumes of ingested fluid may cause concern as, if they are still present in the stomach at the induction of anaesthesia, these may predispose to regurgitation and pulmonary aspiration.
Whatever method is used, overall the administration of oral carbohydrate loading appears safe with no reports of pulmonary aspiration in either large meta-analyses or the estimated five million patients worldwide who have received carbohydrate loading as part of ER programmes.
However, it should be borne in mind that pulmonary aspiration is rare and serious complications and death extremely rare , so very large studies indeed would be required to confirm this.
Probably the most controversial area within oral carbohydrate loading is with patients who have diabetes, whether type 1 diabetes mellitus T1DM with lack of endogenous insulin or T2DM, which is characterized by insulin resistance.
Diabetic patients may tolerate the carbohydrate load poorly, a situation that may then precipitate hyperglycaemia. In addition, if patients have autonomic neuropathy and gastroparesis, they may be at increased risk of having a large residual gastric volume, predisposing to pulmonary aspiration.
These potential disadvantages therefore have to be balanced against the benefits of carbohydrate loading outlined above. There is little evidence to provide definitive guidance. A small study by Gustafsson et al. Although there was a significant rise in serum glucose in the diabetic group There was no evidence of autonomic neuropathy in the diabetic patients, assessed by the co-administration of paracetamol.
One might reasonably expect the impact of carbohydrate loading in T1DM patients to have a greater physiological preoperative upset, but the expected reduction in IR postoperatively may confer considerable benefits to patients. This is a key area in carbohydrate loading, and there is a need for good quality data to address this.
Two areas are worthy of consideration. Firstly, it is possible to control the glycaemic load with insulin and perhaps that is a logical alternative to explore to provide the benefits and limit the hazards of carbohydrate loading.
A second area is whether or not it is possible to reformulate conventional carbohydrate loading into a product that provides the metabolic advantages, but without the same concomitant changes in blood glucose.
Attempts are already underway to explore this latter possibility with the introduction of a glycaemic endothelial drink. It has a lower maltodextrin content and also contains citruline a precursor of arginine , which in turn leads to reduced gluconeogenesis, which may be of value both before and after surgery.
Carbohydrate loading has almost exclusively been studied in elective patients undergoing major surgery, where it has provided tangible benefits. Areas for further research include extrapolating the benefits to other areas of surgery—there is currently a trial under way to evaluate the impact of emergency surgery for fragility hip fracture patients POINT study.
Furthermore, we do not know whether we have the optimal approach in terms of dose and duration of carbohydrate loading and whether or not combining it with other substances such as immunonutrients such as omega-3 fatty acids, glutamine, and arginine , oral nutritional supplements, ketone drinks to conserve carbohydrate and protein stores , or beetroot and other compounds rich in nitrates that supplement production of nitric oxide may provide added clinical improvements.
There is much interest in many of these agents, particularly those rich in nitrates, which have a number of potential benefits to muscle function, such as improved blood flow, mitochondrial efficiency, glucose uptake, and the sarcoplasmic calcium handling, all of which maximize resistance to fatigue, exercise performance, and muscle efficiency.
While anaesthesia has come a long way since the reliance on total overnight fasting, the optimal preoperative drinks are yet to be elucidated. Both authors are Executive Committee Members of The Enhanced Recovery after Surgery ERAS® Society. Professor Ljungvist has advisory board appointment with Nutricia and has received speaking honoraria from Nutricia.
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Carbohhydrate Carbohydrate metabolism and carbohydrate loading Expert. Carbbohydrate D'Agostino, PhD. His research is supported by the Office of Naval Research ONRTreating sun damage of Metaboljsm DoDprivate anf, and foundations. Athletes have Carbohydrate metabolism and carbohydrate loading carbohydrate loading for more than 50 years. And while the popular notion of carb-loading is just cramming down pasta the night before a race, it is actually a systematic approach to athletic nutrition that involves reducing the carbohydrates eaten about a week before an event, followed by eating more carbohydrates than usual in the days before competition. This process helps maximize the amount of glycogen stored glucose in the body on event day.Carbohydrate metabolism and carbohydrate loading -
IR increases occur early and are most marked on the first day after surgery, with large inter-individual variations. It does not necessarily mirror other markers of the stress response such as raised cortisol, growth hormone, and epinephrine. Moreover, IR itself is associated with an increase in complications including the rate of infections and length of stay.
A study by Sato et al. So, if we accept that IR is deleterious, what can we do to restore insulin sensitivity and reduce hyperglycaemia? One approach is to use insulin infusions to control the latter, but altering the pathophysiology upstream in the process is a logical alternative.
The use of minimally invasive surgery, thoracic epidural anaesthesia for open surgery , and early preoperative feeding to reduce the prolonged effects of starvation have a major effect on restoring insulin sensitivity. Another approach is to provide glucose preoperatively, as data from animal models demonstrated that starvation considerably magnified insulin resistance.
Nearly 20 years ago, Ljungqvist et al. With the realization that i. glucose administration conferred significant physiological advantages, it was natural that the oral route would be explored to administer preoperative carbohydrates, with the first study published in Carbohydrate loading is not restricted to surgical patients.
There is a parallel between athletes undertaking a major sporting challenge and elective patient undergoing surgery, as both groups benefit from carbohydrate loading. Physiologically, both groups require an increase in oxygen delivery DO 2 , as oxygen consumption VO 2 rises and if the required increase in DO 2 fails, there is a progressive switch to anaerobic metabolism resulting in a rise in serum lactate concentrations.
In athletes, this results in impaired performance and early fatigue, and in surgical patients there is poorer outcome with increased morbidity and mortality.
There are several practical issues surrounding introduction of carbohydrate preloading. Of note, the evening dose secures glycogen loading with very little, if any, impact on insulin sensitivity prior to surgery.
It is the morning dose that causes changes from the fasted to the fed state, so if patients eat dinner the evening dose may be unnecessary.
Preoperative oral carbohydrate loading has brought many benefits to patients undergoing major elective surgery Table 1. A major—if seemingly somewhat obvious—benefit is generally to improve patient comfort or well-being, 10 with the incidence of various parameters tested such as thirst, hunger, tiredness, malaise, anxiety, and mouth dryness reduced in the oral carbohydrate group.
Interestingly, i. carbohydrates were effective at reducing weakness and tiredness but not thirst and hunger. Table 1 Benefits of oral carbohydrate loading. A key feature is that carbohydrate loading prevents protein loss as measured by urea and 3-methylhistidine excretion with the original data from i.
glucose infusions 12 , as well as the preservation of muscle mass as measured by upper arm circumference 13 , and quadriceps strength at 1 month, 14 both of which suggest that overall muscle function and thus rehabilitation may be improved.
The findings of preserved muscle function, as measured clinically, are not universal and require more study. However, given the current enthusiasm worldwide for implementation of ER programmes vide infra in which rapid return to preoperative physiological function is a key concept, the prevention of further muscle wasting, particularly in those patients with pre-existing frailty and sarcopaenia, is viewed as fundamental.
Weakness causes immobility and vice versa and inevitably leads to poor outcomes. In addition, carbohydrate loading complements the concept of prehabilitation programmes, in which preoperative exercise training improves postoperative muscle function and exercise capacity.
The advent of ER pathways led initially to a focus on length of hospital stay LOS. Carbohydrate loading is a component contributing to ER, and there are many studies looking at its impact within ER programmes. The benefits of oral carbohydrate loading, along with restriction of i. fluids were the two major independent predictors for reducing both adverse symptoms and complications in one report.
Two meta-analyses on carbohydrate loading have provided further data for the adoption of carbohydrate loading. Awad et al. They also confirmed the reduction of postoperative IR but no changes in hospital complications.
A later systematic review published on the Cochrane Database Smith et al. study, unsurprising given that many of the studies were included in both. Smith et al.
demonstrated a smaller reduction in overall LOS 0. There was a lesser impact for patients undergoing orthopaedic and cardiac surgery Fig. It should be borne in mind that both these meta-analyses included studies of varying quality and open to potential bias. Forest plot for carbohydrate loading vs placebo or fasting.
Outcome: length of hospital stay. From Smith et al. A major area of concern for anaesthetists will centre on the safety of carbohydrate loading. Intuitively, significant volumes of ingested fluid may cause concern as, if they are still present in the stomach at the induction of anaesthesia, these may predispose to regurgitation and pulmonary aspiration.
Whatever method is used, overall the administration of oral carbohydrate loading appears safe with no reports of pulmonary aspiration in either large meta-analyses or the estimated five million patients worldwide who have received carbohydrate loading as part of ER programmes.
However, it should be borne in mind that pulmonary aspiration is rare and serious complications and death extremely rare , so very large studies indeed would be required to confirm this.
Probably the most controversial area within oral carbohydrate loading is with patients who have diabetes, whether type 1 diabetes mellitus T1DM with lack of endogenous insulin or T2DM, which is characterized by insulin resistance. Diabetic patients may tolerate the carbohydrate load poorly, a situation that may then precipitate hyperglycaemia.
In addition, if patients have autonomic neuropathy and gastroparesis, they may be at increased risk of having a large residual gastric volume, predisposing to pulmonary aspiration.
These potential disadvantages therefore have to be balanced against the benefits of carbohydrate loading outlined above. There is little evidence to provide definitive guidance. A small study by Gustafsson et al.
Although there was a significant rise in serum glucose in the diabetic group There was no evidence of autonomic neuropathy in the diabetic patients, assessed by the co-administration of paracetamol. One might reasonably expect the impact of carbohydrate loading in T1DM patients to have a greater physiological preoperative upset, but the expected reduction in IR postoperatively may confer considerable benefits to patients.
This is a key area in carbohydrate loading, and there is a need for good quality data to address this. Two areas are worthy of consideration. Firstly, it is possible to control the glycaemic load with insulin and perhaps that is a logical alternative to explore to provide the benefits and limit the hazards of carbohydrate loading.
A second area is whether or not it is possible to reformulate conventional carbohydrate loading into a product that provides the metabolic advantages, but without the same concomitant changes in blood glucose. Attempts are already underway to explore this latter possibility with the introduction of a glycaemic endothelial drink.
It has a lower maltodextrin content and also contains citruline a precursor of arginine , which in turn leads to reduced gluconeogenesis, which may be of value both before and after surgery. Carbohydrate loading has almost exclusively been studied in elective patients undergoing major surgery, where it has provided tangible benefits.
Areas for further research include extrapolating the benefits to other areas of surgery—there is currently a trial under way to evaluate the impact of emergency surgery for fragility hip fracture patients POINT study. Furthermore, we do not know whether we have the optimal approach in terms of dose and duration of carbohydrate loading and whether or not combining it with other substances such as immunonutrients such as omega-3 fatty acids, glutamine, and arginine , oral nutritional supplements, ketone drinks to conserve carbohydrate and protein stores , or beetroot and other compounds rich in nitrates that supplement production of nitric oxide may provide added clinical improvements.
There is much interest in many of these agents, particularly those rich in nitrates, which have a number of potential benefits to muscle function, such as improved blood flow, mitochondrial efficiency, glucose uptake, and the sarcoplasmic calcium handling, all of which maximize resistance to fatigue, exercise performance, and muscle efficiency.
While anaesthesia has come a long way since the reliance on total overnight fasting, the optimal preoperative drinks are yet to be elucidated.
Both authors are Executive Committee Members of The Enhanced Recovery after Surgery ERAS® Society. Professor Ljungvist has advisory board appointment with Nutricia and has received speaking honoraria from Nutricia.
Maltby JR , Sutherland AD , Sale JP , Shaffer EA. Preoperative oral fluids: is a five-hour fast justified prior to elective surgery? Anesth Analg ; 65 : — 6.
Google Scholar. The glycemic index provides insight into how particular foods affect glucose but has limitations. Metabolic Basics. Being aware of these causes of inaccurate data can help you identify—and avoid—surprising and misleading feedback.
Joy Manning, RD. Inside Levels. Levels Co-Founder's new book—Good Energy: The Surprising Connection Between Metabolism and Limitless Health—releases May 14; available for pre-order today. Metabolic flexibility means that your body can switch easily between burning glucose and fat, which means you have better energy and endurance.
Jennifer Chesak. Written By Dominic D'Agostino, PhD. How Does Carb Loading Work? What Kinds of Exercise Does Carb Loading Work For? How can CGM help improve exercise performance? Read the Article. Interested in using a CGM to keep track of your carbs?
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Inside Levels Announcement Announcing: Dr. Metabolic Basics The Explainer What is metabolic flexibility, and why is it important? J Appl Physiol ; — Heigenhauser GJF, Sutton JR, Jones NL. Effect of glycogen depletion on the ventilatory response to exercise.
J Appl Physiol ; —4. Bosch AN, Dennis SC, Noakes TD. Influence of carbohydrate loading on fuel substrate turnover and oxidation during prolonged exercise. J Appl Physiol ; —7. Energy metabolism and prolonged exercise. In: Lamb DR, Murray R, editors. Perspectives in exercise science and sports medicine.
Volume 1: prolonged exercise. Indianapolis: Benchmark Press Inc. Hawley JA, Hopkins WG. Aerobic glycolytic and aerobic lipolytic power systems.
A new paradigm with implications for endurance and ultraendurance events. Sports Med ; 19 4 : — Edwards HT, Margaria R, Dill DB. Metabolic rate, blood sugar and the utilization of carbohydrate. Am J Physiol ; —9. Van den berghe K, Hespel P, Vanden Eynde B, et al.
No effect of glycogen level on glycogen metabolism during high intensity exercise. Maughan RJ, Poole DC. The effects of a glycogen-loading regimen on the capacity to perform anaerobic exercise. Eur J Appl Physiol ; —9. Greenhaff PL, Gleeson M, Maughan RJ.
The effects of dietary manipulation on blood acid-base status and performance of high intensity exercise. Eur J Appl Physiol ; —7. Greenhaff PL, Gleeson M, Whiting PH, et al. Dietary composition and acid-base status: limiting factors in the performance of maximal exercise in man?
Diet-induced acidosis and the performance of high intensity exercise in man. Hawley JA, Dennis SC, Lindsay FH, et al.
Nutritional practices of athletes: are they sub-optimal? J Sports Sci ; S63— Pizza FX, Flynn MG, Duscha BD, et al. A carbohydrate loading regimen improves high intensity, short duration exercise performance.
Int J Sport Nutr ; 5: —6. Sutton JR, Jones NL, Toews CJ. Effect of pH on muscle glycolysis during exercise. Clin Sci ; —8. Galbo H, Holst J, Christensen NJ. The effect of different diets and of insulin on the hormonal response to prolonged exercise.
Acta Physiol Scand ; 19— Brewer J, Williams C, Patton A. The influence of high carbohydrate diets on endurance running performance. Karlsson J, Saltin B. Diet, muscle glycogen, and endurance performance. J Appl Physiol ; —6. Williams C, Brewer J, Walker M. The effect of a high carbohydrate diet on running performance during a km treadmill time trial.
Eur J Appl Physiol ; 18— Widrick JJ, Costill DL, Fink WJ, et al. Carbohydrate feedings and exercise performance: effect of initial muscle glycogen concentration. Download references. Sports Science Institute of South Africa, incorporating the Liberty Life Chair of Exercise and Sports Science, the Medical Research Council and the University of Cape Town Bioenergetics of Exercise Research Unit, Department of Physiology, University of Cape Town Medical School, Cape Town, South Africa.
John A. Hawley PhD, Elske J. Schabort, Timothy D. You can also search for this author in PubMed Google Scholar. Correspondence to John A. Hawley PhD. Reprints and permissions. Hawley, J. et al.
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Microbial resistance properties The Expert. Dominic D'Agostino, PhD. His aCrbohydrate is Carbohydrate metabolism and carbohydrate loading Carvohydrate the Office Hydration and nutrient absorption for young athletes Carbohydrate metabolism and carbohydrate loading Research ONRDepartment of Defense DoDprivate organizations, and foundations.
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In a study published in Cadbohydrate that was sponsored in part by ,oading, my co-authors and I found that athletes who ate a low-carbohydrate diet for 31 days before a shorter, high-intensity athletic event performed the same as when they ate a high-carbohydrate diet for the same period.
These fat-adapted, low-carb athletes performed just as well in a mile run and a series of half-mile sprints as when they were in a high-carb period, and they had lower fasting glucose levels in their blood and more stable levels of blood glucose. During the high-carb dieting period, some of these athletes reached blood glucose levels that were consistent with prediabetes.
Specifically, carb loading has been shown to work for events longer than 90 minutes: Studies from the s found that carb loading led to significantly faster times during the last 10 kilometers of a kilometer race for race walkers. Other studies have found that carbohydrate loading can increase levels of glycogen stores compared to their base levels during normal carbohydrate intake.
In a research review of decades of research on carbohydrate loading, the reviewers concluded that carb loading for events over 90 minutes could improve exercise capacity by 20 percent, and improve times by 2 to 3 percent. Another study showed that adding carbs the day before and morning of the race improved times by 4.
And for shorter cardio events, a low-carb diet may lead to the same performance results as eating a high carb diet over time.
When glycogen stores become depleted, they can also be restored during exercise. In a study of cyclists pedaling for 3 hoursdrinking a sports drink containing 8 percent carbohydrates every 20 minutes helped trained cyclists spare their glycogen stores during the long ride.
In addition, the use of intra-working carb consumption may help in the context of high-volume resistance training. Metabolic health expert Dom D'Agostino, PhD, shares four ways real-time glucose data can help make you a better athlete.
To provide the most benefit, you need to eat the right amount of carbs. During the second phase of carb loading when you consume higher-than-normal amountsathletes may consume as much as 9 to 12 grams of carbs per kilogram of body weight per day.
During the later stages of carb loading, you can facilitate more glycogen accumulation by doing light activity, like taking a short walk. And then the last day or two, you can prevent water retention and bloating if you eat a heavy meal and then go for a light walk: In studies, walks of 30 minutes after meals have been found to stabilize blood sugar after eating.
Not everyone benefits from filling up their glycogen stores before an event, and even if carb loading prevents bonking, the discomfort may not be worth it:.
Levels, the health tech company behind this blog, helps people get CGMs shipped directly to their door, and to understand their data to track meals and performance over time. Click here to learn more about Levels.
Get updates, new articles, exclusive discounts, and more Email Required Comments This field is for validation purposes and should be left unchanged. The Explainer. Research suggests that eating protein and fat first might help reduce your post-meal blood sugar rise. The Levels Team.
Ami Kapadia. Here are healthy sources and ways of eating carbohydrates. Stephanie Eckelkamp. Ultimate Guide. Switching between periods of low- and higher-carb intake may improve performance, gut health, and more.
Find out if a carb-cycling plan is right for you. Zoë Atlas, MPH, RDN. Greg Presto. The glycemic index provides insight into how particular foods affect glucose but has limitations. Metabolic Basics. Being aware of these causes of inaccurate data can help you identify—and avoid—surprising and misleading feedback.
Joy Manning, RD. Inside Levels. Levels Co-Founder's new book—Good Energy: The Surprising Connection Between Metabolism and Limitless Health—releases May 14; available for pre-order today. Metabolic flexibility means that your body can switch easily between burning glucose and fat, which means you have better energy and endurance.
Jennifer Chesak. Written By Dominic D'Agostino, PhD. How Does Carb Loading Work? What Kinds of Exercise Does Carb Loading Work For? How can CGM help improve exercise performance? Read the Article. Interested in using a CGM to keep track of your carbs?
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: Carbohydrate metabolism and carbohydrate loading| New Horizons in Carbohydrate Research and Application for Endurance Athletes | Sports Medicine | Short-term recovery from prolonged exercise. Both authors also read and approved the final manuscript. Article Google Scholar Bishop DJ, Granata C, Eynon N. There are 2 types of fibre: soluble, which dissolves in water and can help lower blood glucose and cholesterol levels, and insoluble, which can help food move through your digestive system, promoting regularity and helping prevent constipation. Biochem J. There are a few different types of carb loading, but all strategies involve increasing the number of carbs you eat and temporarily decreasing the amount you exercise. |
| Carbohydrate loading and metabolism during exercise in men and women | How we reviewed this article: History. Before you start a carb-loading program, there are several common carb-loading mistakes you should be aware of. Christensen EH, Hansen O IV. Nutrition and altitude: strategies to enhance adaptation, improve performance and maintain health: a narrative review. Can J Appl Sports Sci ; 42—6. |
| New Horizons in Carbohydrate Research and Application for Endurance Athletes | We conclude that women did not increase muscle glycogen in response to the 4-day regimen of carbohydrate loading described. In addition, these data support previous observations of greater lipid and lower carbohydrate and protein oxidation by women vs. men during submaximal endurance exercise. authors Tarnopolsky, Mark Atkinson, Stephanie Phillips, Stuart MacDougall, JD status published publication date April 1, has subject area 06 Biological Sciences FoR 11 Medical and Health Sciences FoR Adult MeSH Biopsy MeSH Blood Glucose MeSH Dietary Carbohydrates MeSH Exercise MeSH Fatty Acids, Nonesterified MeSH Female MeSH Glycogen MeSH Humans MeSH Male MeSH Muscle, Skeletal MeSH Oxygen Consumption MeSH Physical Endurance MeSH Physiology Science Metrix Potassium MeSH Respiratory Function Tests MeSH Sex Factors MeSH Urea MeSH published in Journal of applied physiology Journal. keywords Adult Biopsy Blood Glucose Dietary Carbohydrates Exercise Fatty Acids, Nonesterified Female Glycogen Humans Male Muscle, Skeletal Oxygen Consumption Physical Endurance Potassium Respiratory Function Tests Sex Factors Urea. Digital Object Identifier DOI start page end page volume 78 issue 4. About Capability Map Contact Us Index Login Terms of Use. The number of carbs you can eat ranges from 2. If you weighed pounds 70 kg , that would work out to — grams of carbs per day 3. People often use carb loading before certain athletic events or competitions because of the importance of carbs as a fuel source during exercise 4. Specifically, it may be appropriate for exercise that leads to large decreases in the amount of glycogen in your muscles, such as prolonged biking or running 5 , 6. In these types of exercise, fatigue can occur when glycogen levels get too low 7. However, it is probably not effective for shorter durations of exercise or types of exercise that involve short bursts of activity, including weight training 7 , 8 , 9. Summary Your body stores carbs in the form of glycogen. Carb loading is a strategy to increase your glycogen stores and improve exercise performance. There are a few different types of carb loading, but all strategies involve increasing the number of carbs you eat and temporarily decreasing the amount you exercise. Each of these programs is designed to be completed in the days immediately prior to an athletic event or competition. Here are several specific protocols that have been developed over the last 50 years You also reduce exercise on day four and perform no exercise on days five and six. Throughout these six days, you gradually decrease the amount you exercise. During days four to six, you only perform 0—20 minutes of exercise per day. At the beginning of the three days, you perform one exercise session until your body is exhausted This program is identical to the classic three-day program, but you do not perform the exercise session at the beginning. Instead, you simply do not exercise for three days, while increasing the number of carbs you eat Research on this program used a carbohydrate intake of 4. This would be about grams of carbs if you weighed pounds 70 kg. You do not exercise for one day, and you consume a high-carb diet of about 4. Summary There are several specific carb loading programs. The major differences between them are their durations and the amounts of exercise they include. All programs use a short-term high-carb diet while temporarily decreasing exercise. Before you start a carb-loading program, there are several common carb-loading mistakes you should be aware of. Research has found it can be beneficial for exercise lasting more than 90 minutes 3. However, there may be no benefit for slightly shorter durations of exercise, including events lasting 60—90 minutes 7 , 8. Some research found that carb loading with 3 grams per pound 6. Other studies showed that carb loading did not improve performance during high-intensity cycling lasting less than 20 minutes 14 , While fat can be part of a balanced diet , it may be beneficial to limit how much of it you eat during carb loading Eating too much could cause weight gain or leave you feeling sluggish. Some people make the mistake of choosing foods that are high in both carbohydrates and fat, rather than just carbs. For example, many desserts such as chocolate, ice cream and cookies fall into this category, as well as creamy pasta sauces and buttery breads. Checking the nutrition information of foods you eat can help. Eating high-fiber foods could also be detrimental. Although fiber is part of a healthy diet , too much fiber during carb loading can cause stomach discomfort in some individuals Carb loading is a unique time when it could be better to choose white bread or pasta over whole wheat. During this time, you should probably also avoid high-fiber foods like beans. Overall, it may be best to choose lower-fiber carbohydrate sources to avoid the possibility of fullness or stomach discomfort during exercise. Another possible mistake is not knowing if you are eating the right amount of carbohydrates. Without recording what you eat, you may be eating too much or too little. Experts often recommend that people who are carb loading eat 2. Recording your food intake can help you make sure you are eating the right amount 3. However, if you eat more carbs than necessary, you may have changed your diet too much or simply eaten too many calories. As your experience grows, you may not need to do this anymore. However, it is a good idea for beginners. The days before your event or competition are important, and having an upset stomach due to unfamiliar foods can spoil your experience and exercise performance. Because of this, you should choose foods that are familiar to you — in addition to being high-carb, low-fat and low-fiber. If you are considering using carb loading before an upcoming competition or athletic event, there are a few things you should think about. Before you launch into carb loading, consider whether the type and duration of exercise you are doing requires it. If you will be performing exercise lasting more than 90 minutes without breaks, such as running or cycling, you may benefit from this nutrition strategy. If your exercise is shorter or involves many breaks, such as weight training, carb loading is probably not necessary. If you record all the food you eat for several days using a food-tracking app or the nutrition labels on your food, you can calculate your current daily carbohydrate intake. Then you can divide the grams of carbs you eat each day by your weight to compare your current intake to carb loading recommendations. For example, if you weigh pounds 70 kg and you normally eat grams of carbs per day, then you are consuming 1. People who are carb loading may eat 2. That said, experts often recommend a more limited range of 3. Based on these recommendations, you would need to eat approximately double the amount of carbs you would normally. Avoid choosing foods that are high in both carbs and fats, such as desserts, pasta with creamy sauce, pastries and similar items. As discussed, carb loading programs can last from one to six days. It may be a good idea to start with a simple program lasting between one and three days. For example, you could simply increase your carb intake to around 3. You could also practice several different types of carb loading during training and keep notes to decide which helped you feel and perform your best. Generally, it is best to experiment during your training rather than right before a real competition. That way, you can decide what will work best before your big event. Lastly, it may be best to focus on familiar foods during carb loading. Unusual foods could upset your stomach and impair your performance. Commonly recommended foods include pasta, bread, fruits and fruit juices, smoothies, cereals and other high-carb, low-fat foods. Once you have your nutrition plan set, you need to remember to taper your exercise in the days leading up to your event or competition. Summary Before you start carb loading, consider whether you will benefit from it. You should also figure out how many carbs you normally eat so you know how much to change your regular diet. Deciding the right duration for carb loading is also important. Of course, it is also important to have protein to support your muscles. |
| Carb Loading: How to Do It + Common Mistakes | Exercise twice-a-day In-game resource replenishment markers of mitochondrial biogenesis in men. Given the limited knowledge, it is therefore carbohydraate to develop loadiny CHO-loading Carbohydrate metabolism and carbohydrate loading for the Carbohhdrate Carbohydrate metabolism and carbohydrate loading loding 1 diabetes. Forty high-intensity interval training sessions blunt exercise-induced changes in the nuclear protein content of PGC-1 and p53 in human skeletal muscle. Thus, it could be recommended that composite glucose- and fructose-based carbohydrates in a ratio close to unity are ingested irrespective of exercise duration. Article CAS Google Scholar Gejl KD, Nybo L. |
| Carbohydrate loading and metabolism during exercise in men and women | The major issue surrounding a period of starvation needs to be viewed within the context of the pathophysiological changes that accompany major surgery. The stress response describes the process whereby pituitary and sympathetic nervous system activation leads to a number of predictable metabolic changes such as hyperglycaemia, nitrogen loss, and lipolysis. A secondary area is a systemic inflammatory response mediated by various cytokines e. interleukins and tumour necrosis factor. A key area of interest has been surgical stress response modification, for while its evolutionary benefits are evident—substrate mobilization and water conservation when access to food and water is restricted—there is little benefit and indeed much potential harm due to this unmodified pathophysiological upset. Indeed, it has been this approach that has formed the basis for modern enhanced recovery ER pathways. In addition, it is now recognized that anaesthetic and surgical complications such as hypovolaemia, infection, and hypothermia can magnify these changes further. There are many ways of assessing the magnitude of the stress response. These principally include the neuroendocrine sequelae, measuring the hormones themselves—plasma concentration of cortisol, growth hormone, catecholamines, insulin, and so on—or some of the other metabolic changes, in particular hyperglycaemia and nitrogen loss. At the very heart of these changes lies a core physiological disruption: insulin resistance. This resultant IR has been extensively studied and its impact can be considered in two fundamental areas: in the periphery particularly muscle and in the liver. Peripheral IR will reduce glucose uptake leading to hyperglycaemia, whereas hepatic IR will result in an increase in gluconeogenesis. While it has been widely appreciated that previously known diabetic patients have had a poorer outcome than non-diabetic patients, more recently, there has been the recognition that hyperglycaemia in all patients has a significant impact on patient outcome, with an increased length of stay in both the hospital and the intensive care unit, increased rate of infection septicaemia, urinary tract, and lung , myocardial infarction and renal failure, 2 and reoperation and death. This will result in a reduced energy supply to the muscle after operation, with weakness and reduced mobilization. IR has attracted interest for many years outside of major surgery. It is viewed as a precursor to metabolic syndrome and type 2 diabetes mellitus T2DM. Yet its assessment is complex, and there are many methods described to assess IR. These can broadly be divided into two categories: dynamic and simple tests. The gold standard is widely regarded as the hyperinsulinaemic—euglycaemic clamp HEC and is a dynamic test in which a high-dose insulin infusion e. This is administered alongside an i. glucose infusion to maintain normoglycaemia. If serum glucose concentrations remain unchanged, at steady state, the glucose infusion must equal whole-body glucose disposal, sometimes referred to metabolizable glucose M. The amount of glucose infused required for these conditions is typically expressed in milligrams glucose per body mass per minute, with a low value defining IR, whereas subjects without IR require much higher levels of glucose to maintain euglycaemia. Unsurprisingly, this test is very labour—intensive, requiring frequent blood tests with the ever-present risk of hypoglycaemia. As a result, many simpler tests have been described, of which the most common is homeostatic model assessment HOMA in which in fasting plasma glucose and insulin concentrations are measured. As the product of these two measurements decreases, the subject is deemed to be more insulin sensitive i. less IR. Unfortunately, HOMA is often used as a substitute for the clamp method and described as insulin resistance. This is erroneous as the two methods are not interchangeable, with HOMA measuring only basal fasting insulin levels, during which insulin will be inactive. The entire changes causing insulin resistance are thus missed and therefore HOMA gives no insight into the development and magnitude of insulin resistance, with the level of the error increasing with increasing insulin resistance. Other tests have also been described based on an oral glucose tolerance test and often represent better alternatives compared with the HOMA. IR has been extensively studied perioperatively. It increases with the magnitude of surgery, with laparoscopic surgery causing less resistance than minor open surgery, and major open surgery producing the largest increase. IR increases occur early and are most marked on the first day after surgery, with large inter-individual variations. It does not necessarily mirror other markers of the stress response such as raised cortisol, growth hormone, and epinephrine. Moreover, IR itself is associated with an increase in complications including the rate of infections and length of stay. A study by Sato et al. So, if we accept that IR is deleterious, what can we do to restore insulin sensitivity and reduce hyperglycaemia? One approach is to use insulin infusions to control the latter, but altering the pathophysiology upstream in the process is a logical alternative. The use of minimally invasive surgery, thoracic epidural anaesthesia for open surgery , and early preoperative feeding to reduce the prolonged effects of starvation have a major effect on restoring insulin sensitivity. Another approach is to provide glucose preoperatively, as data from animal models demonstrated that starvation considerably magnified insulin resistance. Nearly 20 years ago, Ljungqvist et al. With the realization that i. glucose administration conferred significant physiological advantages, it was natural that the oral route would be explored to administer preoperative carbohydrates, with the first study published in Carbohydrate loading is not restricted to surgical patients. There is a parallel between athletes undertaking a major sporting challenge and elective patient undergoing surgery, as both groups benefit from carbohydrate loading. Physiologically, both groups require an increase in oxygen delivery DO 2 , as oxygen consumption VO 2 rises and if the required increase in DO 2 fails, there is a progressive switch to anaerobic metabolism resulting in a rise in serum lactate concentrations. In athletes, this results in impaired performance and early fatigue, and in surgical patients there is poorer outcome with increased morbidity and mortality. There are several practical issues surrounding introduction of carbohydrate preloading. Of note, the evening dose secures glycogen loading with very little, if any, impact on insulin sensitivity prior to surgery. It is the morning dose that causes changes from the fasted to the fed state, so if patients eat dinner the evening dose may be unnecessary. Preoperative oral carbohydrate loading has brought many benefits to patients undergoing major elective surgery Table 1. A major—if seemingly somewhat obvious—benefit is generally to improve patient comfort or well-being, 10 with the incidence of various parameters tested such as thirst, hunger, tiredness, malaise, anxiety, and mouth dryness reduced in the oral carbohydrate group. Interestingly, i. carbohydrates were effective at reducing weakness and tiredness but not thirst and hunger. Table 1 Benefits of oral carbohydrate loading. A key feature is that carbohydrate loading prevents protein loss as measured by urea and 3-methylhistidine excretion with the original data from i. glucose infusions 12 , as well as the preservation of muscle mass as measured by upper arm circumference 13 , and quadriceps strength at 1 month, 14 both of which suggest that overall muscle function and thus rehabilitation may be improved. The findings of preserved muscle function, as measured clinically, are not universal and require more study. However, given the current enthusiasm worldwide for implementation of ER programmes vide infra in which rapid return to preoperative physiological function is a key concept, the prevention of further muscle wasting, particularly in those patients with pre-existing frailty and sarcopaenia, is viewed as fundamental. Weakness causes immobility and vice versa and inevitably leads to poor outcomes. In addition, carbohydrate loading complements the concept of prehabilitation programmes, in which preoperative exercise training improves postoperative muscle function and exercise capacity. The advent of ER pathways led initially to a focus on length of hospital stay LOS. Carbohydrate loading is a component contributing to ER, and there are many studies looking at its impact within ER programmes. The benefits of oral carbohydrate loading, along with restriction of i. fluids were the two major independent predictors for reducing both adverse symptoms and complications in one report. Two meta-analyses on carbohydrate loading have provided further data for the adoption of carbohydrate loading. Awad et al. They also confirmed the reduction of postoperative IR but no changes in hospital complications. A later systematic review published on the Cochrane Database Smith et al. study, unsurprising given that many of the studies were included in both. Smith et al. demonstrated a smaller reduction in overall LOS 0. There was a lesser impact for patients undergoing orthopaedic and cardiac surgery Fig. It should be borne in mind that both these meta-analyses included studies of varying quality and open to potential bias. Forest plot for carbohydrate loading vs placebo or fasting. Outcome: length of hospital stay. From Smith et al. A major area of concern for anaesthetists will centre on the safety of carbohydrate loading. Intuitively, significant volumes of ingested fluid may cause concern as, if they are still present in the stomach at the induction of anaesthesia, these may predispose to regurgitation and pulmonary aspiration. Whatever method is used, overall the administration of oral carbohydrate loading appears safe with no reports of pulmonary aspiration in either large meta-analyses or the estimated five million patients worldwide who have received carbohydrate loading as part of ER programmes. However, it should be borne in mind that pulmonary aspiration is rare and serious complications and death extremely rare , so very large studies indeed would be required to confirm this. Probably the most controversial area within oral carbohydrate loading is with patients who have diabetes, whether type 1 diabetes mellitus T1DM with lack of endogenous insulin or T2DM, which is characterized by insulin resistance. Diabetic patients may tolerate the carbohydrate load poorly, a situation that may then precipitate hyperglycaemia. In addition, if patients have autonomic neuropathy and gastroparesis, they may be at increased risk of having a large residual gastric volume, predisposing to pulmonary aspiration. These potential disadvantages therefore have to be balanced against the benefits of carbohydrate loading outlined above. There is little evidence to provide definitive guidance. A small study by Gustafsson et al. Although there was a significant rise in serum glucose in the diabetic group There was no evidence of autonomic neuropathy in the diabetic patients, assessed by the co-administration of paracetamol. One might reasonably expect the impact of carbohydrate loading in T1DM patients to have a greater physiological preoperative upset, but the expected reduction in IR postoperatively may confer considerable benefits to patients. This is a key area in carbohydrate loading, and there is a need for good quality data to address this. Two areas are worthy of consideration. Firstly, it is possible to control the glycaemic load with insulin and perhaps that is a logical alternative to explore to provide the benefits and limit the hazards of carbohydrate loading. A second area is whether or not it is possible to reformulate conventional carbohydrate loading into a product that provides the metabolic advantages, but without the same concomitant changes in blood glucose. Attempts are already underway to explore this latter possibility with the introduction of a glycaemic endothelial drink. It has a lower maltodextrin content and also contains citruline a precursor of arginine , which in turn leads to reduced gluconeogenesis, which may be of value both before and after surgery. Carbohydrate loading has almost exclusively been studied in elective patients undergoing major surgery, where it has provided tangible benefits. Areas for further research include extrapolating the benefits to other areas of surgery—there is currently a trial under way to evaluate the impact of emergency surgery for fragility hip fracture patients POINT study. Furthermore, we do not know whether we have the optimal approach in terms of dose and duration of carbohydrate loading and whether or not combining it with other substances such as immunonutrients such as omega-3 fatty acids, glutamine, and arginine , oral nutritional supplements, ketone drinks to conserve carbohydrate and protein stores , or beetroot and other compounds rich in nitrates that supplement production of nitric oxide may provide added clinical improvements. There is much interest in many of these agents, particularly those rich in nitrates, which have a number of potential benefits to muscle function, such as improved blood flow, mitochondrial efficiency, glucose uptake, and the sarcoplasmic calcium handling, all of which maximize resistance to fatigue, exercise performance, and muscle efficiency. While anaesthesia has come a long way since the reliance on total overnight fasting, the optimal preoperative drinks are yet to be elucidated. Both authors are Executive Committee Members of The Enhanced Recovery after Surgery ERAS® Society. Professor Ljungvist has advisory board appointment with Nutricia and has received speaking honoraria from Nutricia. Maltby JR , Sutherland AD , Sale JP , Shaffer EA. Preoperative oral fluids: is a five-hour fast justified prior to elective surgery? Anesth Analg ; 65 : — 6. Google Scholar. Frisch A , Chandra P , Smiley D et al. Prevalence and clinical outcome of hyperglycemia in the perioperative period in noncardiac surgery. Diabetes Care ; 33 : — 8. Kwon S , Thompson R , Dellinger P , Yanez D , Farrohki E , Flum D. Importance of perioperative glycemic control in general surgery: a report from the Surgical Care and Outcomes Assessment Program. Many athletes, recreational or serious, have their pre-event traditions. All-you-can-eat pasta dinners, including unlimited refills of Gatorade, often fill the evening before the big day. Should this be considered just a fun tradition that many recreational athletes make it out to be or is there truly something to saturating muscles stores with glycogen that serious athletes are seeking? Carbohydrate loading is defined as a dietary technique designed to promote significant increase in the glycogen content to delay the onset of fatigue. During high intensity and endurance, carbohydrate is the primary fuel used by the muscles. In lower intensity, carbohydrates may not be the major source of fuel, but they are required for the effective metabolism of fat, which is. Thus carbohydrates are the limiting factor in exercise, meaning when carbs are depleted in either case, performance is dramatically reduced. From any viewpoint, this involves a switch from a normal balanced diet to an extreme. Extremes often stimulate a controversial debate and there thus both a positive and negative side should be weighed up. Some simple facts on carbohydrate metabolism can help you decide to what extent and what method carbohydrate loading may be appropriate for you. The lack of carbohydrates combined with high bouts of exercise during the depletion stage of traditional carbo-loading could elicit hypoglycemia signs are weakness, lethargy, and irritation. Prolonged intense exercise during the depletion stage could also lead to muscle trauma which in fact would impair the storage of glycogen rather than enhance it. Furthermore, carbohydrate loading could lead to the destruction of muscle fibers by excessive glycogen storage. Several lab studies have reported abnormal electrocardiograph patterns in individuals who use the classic method. Besides the irregular heartbeats and sudden loss of blood pressure, diarrhea, cramping, and nausea are often symptoms associated with drastic diet changes. Glycogen is hydrophilic, meaning that it attracts water. This means that with each extra gram of glycogen stored, an extra 3 grams of water is stored too. |
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