Glycogen depletion- How not to exercise
Written By: Milos Pokimica
Medically Reviewed by: Dr. Xiùying Wáng, M.D.
Updated May 29, 2023What happens when we exercise or go on a restrictive diet? What is glycogen depletion and should we avoid it? Does glycogen depletion have any benefits?
What happens to the body is that we go into fasting mode (not starving mode). It is a state that is completely different from starvation.
In the first stage, the body will burn readily available calories in the form of stored sugar glycogen. Same as fat our bodies have storage of ready-to-use sugar (glycogen) that is easily metabolized. It is quick energy that is available in an instant and unlike fat does not require any metabolic pathway. Our cells use glycogen directly.
Most of the sugar is stored primarily in the cells of the liver and the muscles, hydrated with water. When we start to burn more energy than we have available in the bloodstream our blood sugar level is going to drop. At the first stage as a countermeasure, our body is going to use an easily available source of stored energy or in other words stored glycogen. Because glycogen is hydrated with water inside the cells when we burn sugar water molecule is an excess or byproduct of metabolism. Because of that, we will lose some water weight in the first stage.
If you do not know this, you can be surprised when you go on a diet and lose water and be happy, to gain it all back after. Water loss released from glycogen and sodium is usually the culprit for dramatic first-week weight loss.
In the liver, glycogen reserves can build up to 5–6% of the organ’s flesh weight (100–120 grams in an adult). Muscles have a much lower concentration of glycogen, in the range of one to two percent of the total muscle mass.
The untrained individual holds typically about 400 grams of glycogen that is stored in the entire body, in both muscles and the liver. A trained professional athlete can hold double that amount. This amount of glycogen is enough to last for several hours of intensive exercise without replenishment.
When we train our body adapts, and the condition improves. Professional athletes also do something called carbohydrate loading after the exercises to force their bodies to adapt by increasing the storage capacity of intramuscular glycogen stores. There are some studies done on this. If we take caffeine or drink coffee glycogen stores tend to be replenished more rapidly.
Long-distance athletes often experience glycogen depletion. It is called “hitting the wall”. In professional sports, it has a powerful influence because after depleting sugar reserves, fatigue follows and sometimes to the point that it is difficult to move. This is the reason why you see athletes bonking. Bonking (Glycogen depletion) is not the state in which you are just feeling tired. Bonking is when your glycogen reserve stores get so low that your brain starts to run out of energy and then shuts your body down.
After the initial stage and metabolization of easily available reserves of glycogen, the liver will begin to break down fat and protein to form energy immediately. The problem is that this process takes time and until gluconeogenesis kicks in, an athlete may experience symptoms of hypoglycemia. If this happens, it will not be uncommon to see professional athletes collapse from extreme fatigue.
Hypoglycemia comes with dizziness, blurred vision, and hallucinations. Loss of consciousness may also occur under these conditions. The combined use of several different energy sources that allow extended high muscular power outputs that can be maintained for an extended period is a big deal in professional sports and research. Also, no we cannot go on a diet before the marathon to tap into gluconeogenesis and then run. Running a marathon using fat alone as a fuel source is not plausible. If we are able to metabolize fat at a higher rate then we would never become tired and could run indefinitely. The energy efficiency of fat metabolization, unfortunately, is not at that level.
Moreover, our body can only process a limited amount of carbohydrates per hour also, around 30-60 grams depending on individual efficiency. You probably won’t race a marathon, but it is essential to understand how the body works if you want to exercise, you can potentially do yourself damage, or don’t get the desired results.
In bodybuilding, it is a big deal also because catabolizing muscle mass for energy is not the desired course. After glycogen depletion from 16 hours to 72 hours, the body will lean heavily on amino acids and protein catabolism for energy creation. Amino acids will be used, and some of the muscle mass will be lost when going on a fast with or without exercise. We can try to minimize it, but some amino acids will be used for energy.
The loss of some of the tissue is not as bad as it sounds. It has an evolutional purpose and health benefits if done moderately. It is normal for all animals including humans to go into fasting mode periodically. Our bodies have adapted to fasting during evolution in the same way that we have adapted to physical activity. Moderate periodical fasting will help our body to clean its mutated and damaged precancerous cells in a process known as autophagy (self-eating). When there are two cells and one is damaged and one has to be destroyed for energy, the body will catabolize damaged cells first and thus clean itself in a sense. We will have a negative impact on our health if we do not incorporate exercise and fasting into our regular life.
After this initial period, our metabolism will shift to ketosis where it gets almost all of its energy from ketone bodies from fat metabolism. The basal metabolic rate will drop also, or in other words, the use of energy will become more efficient. If you want to diet this is a state you would want to be in. A permanent caloric deficit in the amount that you can handle. Running a marathon or doing extensive exercise in a fast state might not be so beneficial because our brain will be left without food and will be forced to use our own muscle tissue for energy. This is not the desired outcome.
- Feeding – Insulin levels rise during meals. This allows glucose to be absorbed into tissues such as the muscle or brain and used directly for energy. Excess glucose is stored in the liver as glycogen.
- The post-absorptive phase occurs 6-24 hours after fasting begins. Insulin levels begin to drop. Glycogen breakdown produces glucose for energy. Glycogen stores last about 24 hours.
- Gluconeogenesis can take anywhere from 24 hours to 2 days. In a process known as “gluconeogenesis,” the liver creates new glucose from amino acids. This literally translates as “creating new glucose.” Glucose levels in non-diabetics fall but remain within the normal range.
- Ketosis – 2-3 days after fasting begins – The low insulin levels reached during fasting promote lipolysis or the breakdown of fat for energy. Triglycerides, the fat storage form, are composed of a glycerol backbone and three fatty acid chains. Glycerol is used in the process of gluconeogenesis. Many tissues in the body can use fatty acids directly for energy, but not the brain. Ketone bodies, which can cross the blood-brain barrier, are synthesized from fatty acids and used by the brain. Ketones provide approximately 75% of the energy used by the brain after four days of fasting. The two major types of ketones produced are beta-hydroxybutyrate and acetoacetate, both of which can increase by more than 70 percent during fasting.
- Protein conservation phase. High levels of growth hormone help to keep muscle mass and lean tissues in check. The energy required to maintain basal metabolism is almost entirely supplied by free fatty acids and ketones. Increased norepinephrine (adrenaline) levels prevent the metabolic rate from decreasing.
The human body has well-developed mechanisms for dealing with hunger. In essence, what we are describing here is the process of transitioning from burning glucose to burning fat. That is it. Fat is simply stored food energy in the body. When there is a scarcity of food, stored food is naturally released to fill the void. So, no, the body does not ‘burn muscle’ to feed itself until all fat stores are depleted. There will be some catabolism at acceptable levels if you don’t have diabetes. In situations where there is hypoglycemia for survival, our body will burn everything to preserve brain cells from dying. If you don’t have hypoglycemia then no the body will not burn muscle but fat.
We can last for a period of 2.5 to 3 months just drinking water depending on how much fat we have to begin with. If we have large amounts of fat, we can last much longer, but nutrient deficiencies will occur. Because of this reason low-calorie nutrient-dense, whole fiber-rich food is a base for every diet.
A good example of this is a man named Angus Barbieri, who water fasted for an entire year under medical supervision study (Stewart et. al, 1973). He was given vitamin supplements only. No calories, no protein.
References:
- Murray, B., & Rosenbloom, C. (2018). Fundamentals of glycogen metabolism for coaches and athletes. Nutrition reviews, 76(4), 243–259. https://doi.org/10.1093/nutrit/nuy001
- Impey, S. G., Hearris, M. A., Hammond, K. M., Bartlett, J. W., Louis, J., Close, G. L., & Morton, J. P. (2018). Fuel for the Work Required: A Theoretical Framework for Carbohydrate Periodization and the Glycogen Threshold Hypothesis. Sports Medicine, 48(5), 1031–1048. https://doi.org/10.1007/s40279-018-0867-7
- Stewart, W. K., & Fleming, L. W. (1973). Features of a successful therapeutic fast of 382 days’ duration. Postgraduate medical journal, 49(569), 203–209. https://doi.org/10.1136/pgmj.49.569.203
Related Posts
Do you have any questions about nutrition and health?
I would love to hear from you and answer them in my next post. I appreciate your input and opinion and I look forward to hearing from you soon. I also invite you to follow us on Facebook, Instagram, and Pinterest for more diet, nutrition, and health content. You can leave a comment there and connect with other health enthusiasts, share your tips and experiences, and get support and encouragement from our team and community.
I hope that this post was informative and enjoyable for you and that you are prepared to apply the insights you learned. If you found this post helpful, please share it with your friends and family who might also benefit from it. You never know who might need some guidance and support on their health journey.
– You Might Also Like –
Learn About Nutrition
Milos Pokimica is a doctor of natural medicine, clinical nutritionist, medical health and nutrition writer, and nutritional science advisor. Author of the book series Go Vegan? Review of Science, he also operates the natural health website GoVeganWay.com
Medical Disclaimer
GoVeganWay.com brings you reviews of the latest nutrition and health-related research. The information provided represents the personal opinion of the author and is not intended nor implied to be a substitute for professional medical advice, diagnosis, or treatment. The information provided is for informational purposes only and is not intended to serve as a substitute for the consultation, diagnosis, and/or medical treatment of a qualified physician or healthcare provider.NEVER DISREGARD PROFESSIONAL MEDICAL ADVICE OR DELAY SEEKING MEDICAL TREATMENT BECAUSE OF SOMETHING YOU HAVE READ ON OR ACCESSED THROUGH GoVeganWay.com
NEVER APPLY ANY LIFESTYLE CHANGES OR ANY CHANGES AT ALL AS A CONSEQUENCE OF SOMETHING YOU HAVE READ IN GoVeganWay.com BEFORE CONSULTING LICENCED MEDICAL PRACTITIONER.
In the event of a medical emergency, call a doctor or 911 immediately. GoVeganWay.com does not recommend or endorse any specific groups, organizations, tests, physicians, products, procedures, opinions, or other information that may be mentioned inside.
Editor Picks –
Milos Pokimica is a doctor of natural medicine, clinical nutritionist, medical health and nutrition writer, and nutritional science advisor. Author of the book series Go Vegan? Review of Science, he also operates the natural health website GoVeganWay.com
Latest Articles –
Plant Based News
-
Protein Found In Meat Linked To Increased Risk Of Arthritis
on April 12, 2024
-
Try This Easy Quinoa And Edamame Salad
on April 12, 2024
-
Switzerland’s Inaction On Climate Crisis Breaches Human Rights, Says Landmark Court Case
on April 12, 2024
-
Eat At Least 75% Plant-Based Foods, Say Germany’s New Dietary Guidelines
on April 12, 2024
-
Don’t Believe The Myths: The Horse Racing Industry Is Rotten To Its Core
on April 12, 2024
-
South Africa Rules That Vegan Meat Cannot Be Seized From Supermarket Shelves
on April 11, 2024
-
Kale Is One Of The Best Foods We Can Eat – 10 Recipes To Try
on April 11, 2024
Top Health News — ScienceDaily
- Inherited predisposition for higher muscle strength may protect against common morbiditieson April 12, 2024
A study showed that a genetic predisposition for higher muscle strength predicts a longer lifespan and a lower risk for developing common diseases. This is a highly comprehensive international study on hereditary muscle strength and its relationship to morbidity. The genome and health data of more than 340,000 Finns was used in the research.
- A novel machine learning model for the characterization of material surfaceson April 12, 2024
Machine learning (ML) enables the accurate and efficient computation of fundamental electronic properties of binary and ternary oxide surfaces, as shown by scientists. Their ML-based model could be extended to other compounds and properties. The present research findings can aid in the screening of surface properties of materials as well as in the development of functional materials.
- Scientists uncover a missing link between poor diet and higher cancer riskon April 12, 2024
A research team has unearthed new findings which may help explain the connection between cancer risk and poor diet, as well as common diseases like diabetes, which arise from poor diet. The insights gained from this study hold promise for advancing cancer prevention strategies aimed at promoting healthy aging.
- PFAS exposure from high seafood diets may be underestimatedon April 12, 2024
A study suggests that people with diets high in seafood may face a greater risk of exposure to PFAS — the family of human-made toxins known as ‘forever chemicals’ — than previously thought. The researchers stress the need for more stringent public health guidelines that establish how much seafood people can safely consume to limit their exposure, particularly in coastal areas where seafood is frequently eaten.
- Choosing sugary drinks over fruit juice for toddlers linked to risk of adult obesityon April 12, 2024
Consuming sugar-sweetened drinks in the first few years of childhood can be linked to poor diet patterns that increase the risk of obesity in later life, according to a new study.
- Melanomas resist drugs by ‘breaking’ geneson April 12, 2024
A study has disentangled the mechanisms behind one of the ways melanoma cancer cells develop resistance to treatment. The study found that, in response to some drugs, melanomas can ‘break’ parts of their BRAF gene, which is mutated in 1 in 2 melanomas. This helps the tumor create alternative versions of the protein which lack regions targeted by one BRAF inhibitors, one of the main drugs used to treat this type of cancer, making treatment less effective. The findings pave the way for […]
- Cells putting on a faceon April 12, 2024
Neural crest cells — embryonic pluripotent cells within the facial primordium — may be necessary for forming proper animal facial structures. Researchers have produced neural crest cell-rich aggregates from human pluripotent stem cells and developed a method to differentiate them in cell populations with a branchial arch-like gene expression pattern.
PubMed, #vegan-diet –
- Changes in the consumption of isoflavones, omega-6, and omega-3 fatty acids in women with metastatic breast cancer adopting a whole-food, plant-based diet: post-hoc analysis of nutrient intake data…on April 5, 2024
CONCLUSION: Transitioning to a WFPB diet resulted in significantly increased isoflavone intake and decreased n-6:n-3 ratio in women with breast cancer.
- A whole food, plant-based randomized controlled trial in metastatic breast cancer: feasibility, nutrient, and patient-reported outcomeson March 30, 2024
CONCLUSIONS: Significant dietary changes in this population are feasible and may improve QOL by improving treatment-related symptoms. Additional study is warranted.
- Restrictive Diets in Patients with Fibromyalgia: State of the Arton March 28, 2024
Around 20-30% of Fibromyalgia patients modify their dietary habits after diagnosis, including avoiding certain food groups such as cereals. In this systematic review, we used the PRISMA guidelines to select the main studies that have evaluated the effectiveness of restrictive diets, including elimination and vegetarian diets, in patients with Fibromyalgia. Data on vegetarian/vegan diets are more consistent than data on elimination diets due to higher quality and better results of the […]
- Dietary Intakes of Long-Chain Polyunsaturated Fatty Acids and Impulsivity: Comparing Non-Restricted, Vegetarian, and Vegan Dietson March 28, 2024
CONCLUSIONS: The significantly lower omega-3 LCPUFA dietary intakes in the vegan diets were associated with higher scores in the second-order attentional aspect of self-reported impulsiveness.
- Impact of iodine supply in infancy and childhoodon March 28, 2024
PURPOSE OF REVIEW: To assess the most relevant articles on the impact of iodine supply in at-risk populations, namely infants and young children, pregnant and lactating women.
Random Posts –
Featured Posts –
Latest from PubMed, #plant-based diet –
- Fruit Quality Assessment of Novel Hybrid Pummelo × Sweet Orange and Its Molecular Characterization Using Acidity Specific Markersby Raushan Kumar on April 11, 2024
RESEARCH BACKGROUND: There is considerable diversity in newly developed pummelo × sweet orange citrus hybrids. Most hybrids showed lower peel thickness and high juice yield but there is a lack of information on fruit quality parameters and molecular characterization. Therefore, the aim of the current study is to determine the content of antioxidants and properties of the fresh juice of 24 new pummelo × sweet orange citrus hybrids (Citrus maxima [Burm. f.] Osbeck × Citrus sinensis [L.] […]
- Environmental conditions affect the nutritive value and alkaloid profiles of Lupinus forage: Opportunities and threats for sustainable ruminant systemsby Ana R J Cabrita on April 10, 2024
The identification of crops that simultaneously contribute to the global protein supply and mitigate the effects of climate change is an urgent matter. Lupins are well adapted to nutrient-poor or contaminated soils, tolerate various abiotic stresses, and present relevant traits for acting as ecosystem engineers. Lupins are best studied for their seeds, but their full foraging potential needs further evaluation. This study evaluated the effects of location and sowing date on forage production,…
- Stronger together than apart: The role of social support in adopting a healthy plant-based eating patternby Robin Ortiz on April 10, 2024
The influence of the social environment on health behaviors is well documented. In recent years, there is mounting evidence of the health benefits of a plant-based eating pattern, yet little is known about how the social environment impacts the adoption of a plant-based eating pattern, specifically. In this convergent parallel mixed-methods study, we analyzed quantitative survey data and qualitative focus group data to assess how social support impacted participants of a lifestyle medicine…
- Simultaneous detection of mycotoxins and pesticides in human urine samples: A 24-h diet intervention study comparing conventional and organic diets in Spainby Jose A Gallardo-Ramos on April 10, 2024
Pesticides and mycotoxins, prominent chemical hazards in the food chain, are commonly found in plant-based foods, contributing to their pervasive presence in the human body, as evidenced by biomonitoring programs. Despite this, there is limited knowledge about their co-occurrence patterns. While intervention studies have demonstrated that organic diets can significantly reduce pesticide levels, their impact on mycotoxin exposure has been overlooked. To address this gap, this study pursued two…
- Plant-based meat analogues (PBMAs) and their effects on cardiometabolic health: An 8-week randomized controlled trial comparing PBMAs with their corresponding animal-based foodsby Darel Wee Kiat Toh on April 10, 2024
CONCLUSIONS: A plant-based meat analogues diet did not show widespread cardiometabolic health benefits compared with omnivorous diets over 8 weeks. The composition of PBMAs may need to be considered in future trials.
- Adherence to the Mediterranean diet in two Moroccan populations living at different distances from the Mediterranean Seaby Mohamed Mziwira on April 8, 2024
CONCLUSION: The study data indicate that Mediterranean Diet is far from being a global pattern in this Moroccan population. The study draws attention to the need for a promoting intervention to maintain this pattern as the original diet in the region.