Low Carb Diets: Part 3
The metabolism is regulated in all of its physiological and biochemical processes by a group of extremely biologically potent compounds called hormones. In general, there are five hormone systems that govern the processes of energy input and output. The Insulin/Glucagon system, the Testosterone-Estrogen/Cortisol system, the Growth Hormone/IGF system, the Catecholamine or Adrenaline system and the Thyroid system. All of these are interactive and interdependant, and the conditions in one system are often related to the conditions in the other systems.
Besides assisting in the storage and utilization of glucose, insulin does the same to amino acids and fats. This means that whenever insulin is released, you are storing fat. The substance that causes the greatest release if insulin is glucose. Any time carbohydrates are ingested, they are broken down to glucose, and insulin is released. The rate at which a carbohydrate is broken down and absorbed into the blood is measured on a scale known as the Glycemic Index or GI. In general, the higher the GI of a carbohydrate, the greater the amount of insulin that will be released upon its absorbtion.
Other factors that affect the rate and magnitude of insulin release include the amount of carbohydrate, the presence of protein (the combination of protein and carbohydrate causes greater increases in insulin levels than carbohydrates alone), the frequency and regularity of feeding, the length of time between feedings (the longer between feedings, the lower glucose levels will drop and the higher they will rise after feeding), the fitness of the individual and overconsumption of refined carbohydrates that has led to insulin resistence.
People who overconsume carbohydrates tend to have higher resting insulin levels. This means that not only are they storing excess carbohydrate as fat, but the entire fat storing procress is being reinforced by the presence of insulin. In fact, chronic overconsumption of carbohydrates can lead to a blunting of the entire insulin mechanism, such that target cells become resistent to insulin and no longer act to allow access to glucose. This causes glucose accumulate and rise in the blood, causing more insulin to be released. All of this encourages the process of obesity, and eventually the insulin resistence can progress to full-blown Type 2 adult-onset diabetes.
By reducing dietary carbohydrate levels, the level of insulin can be minimized, and its fat storing effects can be reduced. This is the scientific principle that is the foundation of low carbohydrate diets. Obviously, this principal applies mostly to individuals who consume large quantities of refined and simple carbohydrates, and not everyone can benefit from carbohydrate reduction. Individuals who do not overconsume carbohydrates or who consume carbohydrates that are low on the GI may find a low-carbohydrate diet not only ineffective, but counterproductive as well. Testosterone, estrogen and cortisol are all steroid hormones. Although their physiology and biochemistry are quite dissimilar, they can be viewed as functioning together to support the two opposite sides of the metabolism.
Testosterone and estrogen function in support of Anabolic processes. These include the processes that function in tissue building and repair and energy storage, like muscle building and tissue repair and secondary gender-associated characteristics (ie.muscle mass in males and softer skin in females). Cortisol functions in support of Catabolic processes. These include the processes that function in tissue breakdown and energy use, like breaking down and removing damaged tissue to allow new tissue to be built, or breaking down stored fat to use for energy.
Testosterone and estrogen differ in their regulation of secondary gender-associated characteristics. For the purposes of this discussion, we will focus on their opposite effect on fat: testosterone promotes mobilization of fat and estrogen promotes storage of fat. This means that in general males tend to be naturally leaner than females.
Cortisol, produced in the adrenal cortex, is known as the 'stress' hormone. It acts as an insulin antagonist, promotes fat and protein breakdown, conserves glucose and it causes an increase in gluconeogenesis. Unfortunately, the body tends to break down its muscle tissue to obtain amino acids for the gluconeogenic process. In this way, muscle can be viewed as a storage form of amino acids, readily made available to make up for a lack of carbohydrate. However, for the purpose of fat loss, losing muscle is a problem, since, in fact, muscle burns fat and losing muscle can lead to a reduction in Resting Metabolic Rate (RMR). So, although cortisol does act to mobilize stored fats, its presence also encourages muscle wasting.
On one hand, it can save our lives during periods of starvation, but it acts as a 'double-edged sword' for people interested in long-term weight loss and dieting. This is where the muscle-preserving and building effects of resistence training can be of great use. It should be noted that building muscle requires the presence of enough glucose to prevent muscle wasting due to gluconeogenesis. Also, resistence training draws heavily on glycogen stores, and training can suffer if these stores become chronically depleted.
Therefore, a post-workout recovery meal/shake should include carbohydrates (and protein!), in order to refuel glycogen stores after training and to promote muscle building. The amount of post-workout carbohydrate that is required depends mainly on the type, duration and intensity of training. It should also be noted that if the post-workout meal/shake is low in fat, the likelihood that this meal will lead to fat storage is very low, despite any increases in insulin level following the ingestion of the carbohydrate.
The other steroid hormones, testosterone (produced in the testes of men and produced as dehydroepiandrosterone in the adrenal cortex in both sexes) and estrogen (produced in the ovaries of females and in the adrenal cortex of both sexes) are less affected by carbohydrate levels, and more affected by dietary fat intake. In this case, the law of supply and demand applies. The steroid hormones are all derived from the same basic building block, another steroid compound known as Cholesterol. Cholesterol is obtained in the diet from animal sources (meats, dairy), but we possess the metabolic pathway to build it from fat, and thus from any macronutrient. This metabolic pathway is dependent on the intake of fat, therefore it slows down when dietary fat is low, and less steroid hormone is produced. This affects both testosterone and estrogen.
Women are less affected by this since they tend to be higher in bodyfat than men, although there are incidences where female athletes and female bodybuilders cease to menstruate because of lack of available female hormones. Men, on the other hand, can be greatly affected by their intake of fat. In a diet of 15% fat or less, there can be a decrease in testosterone production and in a diet of 40% fat, there can be an increase in testosterone production. If carbohydrates are resticted along with fat, there is a fairly great risk of muscle wasting. If cortisol levels rise while testosterone levels drop, the relative amount of muscle wasting will be greater than if testosterone levels are maintained or even increased.
Testosterone provides a natural mechanism to protect against the fat storing effects of insulin and the muscle wasting effects of cortisol. It is to the advantage of anyone interested in losing fat, to maximize the potential support provided by testosterone. Reducing dietary fat too low can lead to a reduction of testosterone, especially in men. In general fat should be kept between 15% and 40% of the total caloric intake to prevent testosterone reduction. Resistence training will also increase testosterone levels in men, but not to any great extent in women. Even if the relative increase in testosterone levels associated with resistence training will be greater in men than in women, women can still benefit greatly from resistence training.
Estrogen, the 'female' hormone, poses an unfair disadvantage for women trying to lose fat. Although it is not directly responsible for fat storage like insulin, it is nontheless responsible for the type of fat deposition that is associated with female gender characteristics. For example, insulin might be responsible for increasing storage of fat around the hips, thighs, buttocks, abdomen and other typically female fatty areas, but estrogen is responsible for directing storage to these areas. In combination, estrogen and insulin create quite a potent fattening mechanism. Add to that lack of physical activity and you have a powerful ct weight-gain formula. Regular physical activity, including resistence training, combined with some form of glycemic control dietary protocol can greatly affect fat loss in women.
The Growth Hormone (GH)/Insulin-like Growth Factors (IGF) system is the fat-loss/muscle-building/low carbohydrate superformula. GH, produced in the anterior pituitary gland, has the following actions: it decreases glucose utilization, decreases glycogen synthesis, increases amino acid transport across cell membranes, increases protein and collagen synthesis, increases breakdown and utilization of fatty acids, increases availability of glucose and amino acids, stimulates cartilage growth, increases retention of nitrogen, sodium, potassium and phosphorus.
GH gives ideal metabolic support for a low-carbohydrate dietary protocol. It spares glucose, mobilizes and burns more fat, builds muscle, tendons, ligaments and cartilage and sets up good nutritional conditions for repair of tissues. In general growth hormone is released in pulses at intervals during the course of 24 hours. There is a large degree of variability with respect to the frequency and intensity of these pulses. Generally, females have higher resting levels of GH than men, and so perhaps mother nature has compensated for higher estrogen levels by giving women higher GH levels.
Several factors are known to cause the release of GH. These include fasting, low blood glucose, stress, injury or trauma, fever, and dopaminergic agents (Neurotransmitters). Resistence training can increase the production of GH. In particular, lactic acid acts as a potent stimulus for the release of GH. Resistence training protocols that produce greater amounts of lactic acid tend to increase GH production. Also, GH production is greatest during Slow Wave Sleep (SWS). Missing sleep can disrupt normal circadian rhythms, and this can lead to a reduction of the GH that is released during SWS.
One of the ways that GH acts is through a group of intermediate messenger proteins collectively known as Insulin-like Growth Factors or IGF's. In particular, IGF-1 is the messenger known to be active in protein synthesis in cells. This is another factor which can be instrumental in the prevention of muscle wasting associated with hypocaloric and especially low-carbohydrate dietary protocols. IGF-1 is sensitive to feeding protocols, especially when an individual engages in multiset resistence training. Studies have shown that pre and post workout carbohydrate/protein supplementation leads to greater increases in IGF-1 values, illustrating the need for appropriate supplementation to fully support and optimize fat loss through diet and exercise.
The Adrenaline or Catecholamine system is also known as the 'fight or flight' system. It includes the Catecholamine hormones adrenaline, noradrenaline and dopamine. Adrenaline primes our body for stress and physical activity. Examples of some of its actions include increased transmission of nerve impulses, dilation of blood vessels in working muscles, increased heart rate, elevated blood pressure, mobilisation of fat and glucose, and constriction of blood vessels leading to organs of the digestive tract.
It should be noted that many of the actions of the adrenaline system can take place in the absence of physical activity. Stress, emotions, anticipation of movement can all causes an increase in the adrenaline response in the absence of physical activity. Chronic stress can lead to a state of chronically elevated adrenaline, which in the absence of physical activity and the ensuing 'rest and recovery' period, and cause a whole range of physical and psycological health problems. The Sympathetic and Parasympathetic divide the nervous system into two antagonistic main branches, which represents the two sides of a very ancient survival mechanism. When the level of adrenaline rises above a specific threshold value, it acts upon the sympathetic nervous system to engage the 'fight or flight' system, and when the adrenaline level drops below a specific threshold, the parasympathetic system will re-engage, and the body will settle back down to 'rest and recover'. An easy way to capitalize on the energy using effects of adrenaline is to wait for an hour after stopping cardiovascular exercise before eating. This allows the adrenaline system to taper down slowly, so that you can capitalize even further on its calorie burning effects.
Engaging the sympathetic system often means the suppression of the parasympathetic system. For example, digestion of food will slow to a halt in favor of the 'fight or flight' response, so that if food is eaten right before or during exercise, it will remain undigested, and physiological priority will go to the processes involved in physical activity. This is why you shouldn't eat right before swimming.
Also, food can interfere with the adrenaline system. Ingestion of a high GI carbohydrate right before or during physical activity will cause the release of insulin, which will interfere with the processes of energy mobilization and utilization, and it can cause an individual to feel sluggish and physically weak, as though they are working against the grain. As long as activity continues, the adrenaline system will continue to try and dominate the metabolim in direct opposition to insulin. Once physical activity ceases, ingested food coaxes the body from a state of 'fight or flight' to a state of 'rest and recovery'. However, an 8% glucose solution can be absorbed without causing a rise in insulin, and ultra-endurance athletes often rely on these to prevent glycogen depletion.
The Thyroid system, consisting of the protein-iodine hormones Thyroxine (T4) and Triiodothyronine (T3), acts to regulate the Resting Metabolic Rate (RMR). It governs all the other systems by adjusting energy expenditure in such a way that is not affected directly by diet. Although thyroid production responds to overall energy intake in its regulation of RMR, it does so within genetically predetermined parameters that limits the effects of outside influences like diet.
Similar to the actions of other systems and hormones, the RMR is kept within a specific range by the constant secretion/feedback of the thyroid hormones. When the metabolic rate drops below a specific threshold value, the output of thyroid hormones increases and the RMR increases. When there is a chronic increase in the RMR, the output of thyroid hormones decreases and the RMR drops. Three percent of obese people suffer from an abnormally functioning thyroid gland. In these individuals, thyroid output is abnormally low, and weight gain is a result of an abnormally slow RMR.
The RMR is held fairly constant throughout one's lifetime. Exercise can increase energy output even at rest, and thus affects the RMR. Resistence exercise that increases muscle mass causes an increase in daily energy expenditure in support of the extra muscle tissue. More muscle spends more energy. In fact, this is one of the best ways that an individual can affect the RMR. Aerobic exercise increases the efficiency and fluidity of all the energy using pathways. Individuals who engage in regular aerobic activity have higher RMR values than untrained individuals of the same lean body mass. By combining resistance and aerobic exercise, an individual can maximize their natural RMR.
Conclusions - to carb or not to carb
It should be clear that carbohydrate restriction is not necessarily the ideal way to achieve fat loss, and can even be counterproductive. The potential for ketoacidosis (see part 2 of this article) and muscle wasting, the looming risk of heart disease and the discomfort and inconvenience tend to outweigh the possible benefits.
However, in conjunction with exercise, carbohydrate restriction can be useful in individuals who chronically overconsume them, at least in the short term. In the long-term, even carb addicts should eventually reintroduce low GI or 'smart carbs' back into the diet. Anyone else should design their protocol around a mixed diet based on an energy deficit, where portion sizes are reduced. Also relying on low GI carbohydrates or 'smart carbs' can be a simple and effective way for anyone to improve glycemic control.
If you still really want to cut carbs, cut them at night. This can be useful for people who have developped the habit of late-night snacking (especially carb addicts), skipping breakfast, skipping lunch, not eating all day, eating a huge meal at night or any combination of these. All of these scenarios have the potential for causing an insulin nightmare. Besides, reducing insulin secretion, cutting carbs at night also tends to leave the appetite unsatiated, so that you will ultimately be hungrier in the morning. Eating a larger breakfast will give you enough energy to get through your day productively, and you will be less hungry at night. Essentially, cutting carbs at night can help you reset your appetite. As long as enough carbohydrates are consumed during the day, eliminating them at night will not only pose absolutely no health risks, but may actually be beneficial. During sleep, we are protected from ketoacidosis and muscle wasting by the carbohydrates that were eaten during the day and by the glucose sparing effects of GH released during SWS.
It may be fairly evident that the delicate interpay between all of the metabolic variables is very complex, and the degree of individual variation is probably infinite.With this in mind, it seems fairly logical to assume that no two people will react the same way to any given protocol, and that there is no single 'magic' solution for everyone. But what about all those diets and all those people who lost all that weight? They are not you. You have to experiment with your own body and see how it responds to different combinations of diet and exercise. Understanding your particular metabolic idiosyncracies is a lifelong process of self-discovery, and it can be fun and very rewarding. Take notes, be honest and accurate, don't be rigid or overly-strict with yourself, don't be afraid to change your routines when necessary, and be patient. Learn as much as possible about the underlying scientific principles behind dietary modification and exercise so that you can apply them properly. Don't be afraid to enlist the advice of a registered dieticien, nutritionist or fitness professional.
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Sam Torontour, B.Sc., C.S.C.S. is an experienced personal trainer and certified strength and conditioning specialist with over 15 years experience as a fitness professional. With a Bachelor of Science degree in Exercise Science and a minor in Biology from Concordia University, he possesses a thorough scientific understanding of the workings of the human body, nutrition and exercise.
He is certified by the National Strength and Conditioning Association (NSCA) as a Certified Strength and Conditioning Specialist (CSCS) and has expertise in a wide variety of areas. His specialties include physique transformation, athletic preparation, muscle balance and posture, flexibility, nutrition and supplementation. He is also an instructor of Muay Thai (an ancient martial art developed in Thailand). He has worked with males and females of all ages and from all walks of life, including students, older adults, teens and professionals. He is presently working at Gym L’Apogée on St. Laurent Boulevard in Montreal, and also works with clients at their homes.