I receive lots of questions regarding the eating of carbohydrates and one of the general questions that I frequently get asked is “wont carbohydrate foods make me fat?". This is not the case. Carbohydrates are an energy food for the body, and are stored in your muscle and liver for use by the body. The carbohydrates are used by every cell in your body, used by the brain, used for moving muscles, whatever you do the glucose in the blood from carbohydrates are used to fuel that activity.
Most carbohydrate foods come from plant-based sources. The typical sources of carbohydrates that we eat include:
- Peas (legumes).
Some animal foods contain a significant amount of carbohydrates, such as milk and other dairy foods. There are different types of carbohydrates such as simple and complex, with the simple carbohydrates being digested quickly. Simple carbohydrates food sources include, table sugar, fruits, sweets, soft drinks, and things like cakes and biscuits.
The complex carbohydrates include fiber, which is required for healthy bowel function, and can make you feel fuller for longer due to fiber absorbing water, which increases the bulk of the waste matter. This also makes the waste softer and increases the speed and ease with which it passes through the bowel. In addition, soluble fiber helps to stabilize blood sugar levels because it slows down the rate at which glucose is absorbed into the blood stream. It also helps to lower blood cholesterol levels, which is important for reducing the risk of heart disease. Also the feeling of fullness which fiber produces can help people who are trying to lose weight to control their appetite.
Some plant-based foods will contain more fiber than others. Good sources of fiber are fruit, vegetables, wholegrain rice/pasta, wholemeal bread, many breakfast cereals, nuts, seeds and bran. Particularly good sources of soluble fiber are fruit, vegetables, beans, and oats. Other complex carbohydrate food sources are classed as starch such as bread, cereal, potatoes, pasta, rice, and legumes (dried peas and beans) vegetables, seeds.
Do We Need Carbohydrates to survive?
Carbohydrates are the nutrients that we need in the largest amounts. According to published articles, 45%-65% of our total calories should come from carbohydrate intake. We need this amount of carbohydrates because they are the body’s main source of fuel. They are easily used for energy. All the tissues of the body can use glucose for energy. They are needed for the central nervous system and also the kidneys, brain and muscles (including the heart) to function properly. Carbohydrates can be stored in the muscles and liver (glycogen) and later used for energy.
In absence of glycogen for fuel the body will then
initially use protein from muscle tissue.
The Side Effects of a Low Carbohydrate Diet.
The low carb diet has been reported to be the main diet to lose fat. But this type of dieting can have side effects. One of the main side effects is depletion of muscle glycogen and as glycogen is stored with water this also goes which can lead to dehydration. People associate the weight loss from loss of water as fat loss, but this is not the case.
Another serious side effect that will affect your training goals is that on a low carbohydrate diet you will fatigue earlier which in turn leads to feeling lethargic and you don’t feel like training. This then leads to lack of exercise and will lower the metabolic rate. Muscle glycogen is the normal fuel choice for your muscle and without glycogen the muscle fibers contract less when glycogen is not immediately available to the working muscle. In absence of glycogen for fuel the body will then initially use protein from muscle and fat, the initial phase of your muscle depletion will be rapid and caused by the use of easily accessed muscle protein for metabolism or for conversion to glucose for fuel. If you then eat an excess of protein this does not prevent this because there is a caloric deficit.
A very important part of the low carbohydrate diet to remember is that when insulin levels are chronically low the catabolism of muscle protein increases and much needed protein synthesis stops. Another side effect of this type of diet is the muscles and skin lack tone and become saggy. Saggy muscles and skin doesn’t look good and you lose the healthy, vibrant look even if you have lost some fat.
Low carbohydrate diets are also a high fat diet which is not healthy. There are research studies that have been done that says that an increase in the consumption of animal products and/or saturated fat leads to increased incidences of heart disease, strokes, gall stones, kidney stones, arthritic symptoms, certain cancers etc. Fat is certainly necessary, and desirable in your diet, but they should be mostly healthy essential fats and taken in moderation. Processed foods/synthetic low fat foods with loads of added sugars are not the answer. And neither are foods with artificial sweeteners or added fat. The use of artificial sweeteners has never been shown to aid in weight loss and their use may also cause health problems. Another problem with embarking on a low carbohydrate diet is the lack of sufficient quantities of the nutrients, phytonutrients and antioxidants that are found in legumes, vegetables, whole grains and fruits. These nutrients are even more important when on a high protein, low carbohydrate diet.
Turning Glucose into Glycogen.
After a meal, blood glucose levels rise, the pancreas is the first organ to respond. It releases the hormone insulin, which signals the body’s tissues to take up surplus glucose. From some of this excess glucose, muscle and liver cells build glycogen. The muscles hoard two thirds of the body’s total glycogen and use it just for themselves during exercise.
The liver stores the other one third and makes this available as blood glucose for the brain and other organs when the supply runs low. Glycogen is designed for its task of releasing glucose on demand. When blood glucose levels drops and cells require energy, a pancreatic hormone, glucagon, floods the bloodstream. Thousands of enzymes within the liver cells then respond to release a surge of glucose into the blood for use by all the other body cells. Another hormone, epinephrine, does the same thing as part of the body’s defense mechanism in times of danger.
Conversion of Excess Glucose to Fat.
Sustained high glucose intake in the diet leads to increased fat synthesis. If glucose intake continues after muscle and liver glycogen stores are saturated, the glucose is not excreted or wasted. It is converted to a fuel storage form which has an unlimited capacity. I.e. triglycerides stored in adipose tissue. Glucose is converted to pyruvate by glycolysis. The pyruvate is converted to acetyl CoA, which is the starting material for the synthesis of fatty acids. This synthesis occurs in the liver followed by conversion of the fatty acids to triglycerides (also in the liver) and then transport to adipose tissue for storage. Triglycerides (fat) form the major energy store in the body.
You should avoid all processed (refined) carbohydrates as the processing strips away the nutrient density of the food and rendering it an empty calorie that contributes very little to cellular function.
So Which Carbohydrates Should we Eat?
Firstly we should omit the foods that we shouldn’t eat like sweets, candy, biscuits, cakes, pastries, baked goods, processed and refined foods like white breads, pastas, white rice, and basically any foods with added sugars. The main type of carbohydrates that you should be eating are the nutrient dense types, these are the ones that contain the vitamins, minerals as well as fiber. Not only are the nutrient dense carbs insulin friendly, but they also supply your body with essential compounds that enhance metabolic function.
Many of the vitamins and minerals contained in the carbohydrates are also co-factors that assist the body in fat burning. Others serve as antioxidants that keep the body cells working optimally. The fiber promotes satiety, which decreases the urge to overeat. The nutrient dense carbs include whole grains, vegetables and fresh fruits. You should avoid all processed (refined) carbohydrates as the processing strips away the nutrient density of the food and rendering it an empty calorie that contributes very little to cellular function. Eating these types of foods triggers the pancreas to release large amounts of insulin which in turn turns on the fat storage enzymes while shutting down the enzymes that are responsible for fat burning. This increases the chances of gaining excess body fat.
When considering adding grains to your diet, then choose the brown variety, foods like brown rice, whole grain pasta, and multigrain breads avoiding the white types of these foods. Brown carbohydrates foods are slower burning which ensures that glucose enters the circulation much slower, which means that insulin will remain stable and the potential for fat storage is lower. For vegetables choose the green variety whenever possible, as these are extremely low in calories and can be consumed in large amounts. Other vegetables such as corn, peas, and squash have a higher caloric content, but can be eaten in moderation. With regard to fruits avoid the canned variety as these are normally sweetened. Also limit fruit juices as these normally contain less fiber than ordinary fruits and less vitamins and minerals. Remember also that liquids pass through the stomach very quickly which in turn can cause an increase in blood sugars and insulin levels. So also limit fruit juices.
Importance of Post-workout Carbohydrate Intake.
The post workout meal is the most important meal that someone who is a weight trainer can eat. As mentioned above glycogen is depleted during your training and the liver and muscles are craving nutrients. The release of an enzyme glycogen synthase becomes activated; it is this enzyme that is involved in promoting glycogen storage. This enzyme release and a combination of other transporters facilitate the rapid intake of glucose allowing glycogen to be replenished at an accelerated rate.
But a two hour delay in carbohydrate consumption can reduce the amount of glycogen resynthesis by 50%, so the need to get carbohydrates within 1 hr is crucial. It may take up to 20 hrs for glycogen stores to become replenished depending on the amount of glycogen used in training. The consumption of moderate to high glycemic index carbohydrate foods have been shown to rapidly provide glucose to muscles immediately after training but studies have shown that low glycemic carbohydrates do not provide the same rapid glucose rise. So the intake of carbohydrate immediately after training is highly recommended but studies have also shown that consuming some protein post training is also beneficial. The protein and carbohydrate mixture both stimulate an insulin secretion which helps in glycogen resynthesis but with the added protein to this meal supplies amino acids to the trained muscle. A recommended amount of carbohydrates immediately after training is at least 1g of carbohydrates per kilogram of bodyweight. The consumption of a whey protein works best after training due to it being rapidly assimilated and reaching the muscles quickly at a time when the muscles are primed for anabolism which means that all of the protein will be utilized for muscle repair with little waste. Fluids are also very important as water is stored in the muscle along with the carbohydrate. So don’t neglect your water intake.
How Much Carbohydrate Do We Need?
Each gram of carbohydrate provides 4 calories. You need anywhere from 40-60% of your calories from carbohydrate. There is no specific Recommended Daily Allowance (RDA) for carbohydrate. Glucose is more efficiently oxidized than fatty acids of equal carbon chain length and can be utilized under both aerobic and anaerobic conditions. Consequently, a minimum of 50% of total energy consumed should be digestible carbohydrate. Increasing muscle activity requires adequate fuel supply for ATP synthesis by muscle. When muscle activity is anticipated, the adrenal glands secrete adrenaline. Adrenaline increases muscle glycogen degradation (by activating the breakdown enzymes and de-activating the synthesis enzymes). When muscle activity ceases, adrenaline secretion is switched off. When glucose becomes available again after a meal glycogen stores in muscle are replenished. Glucose can only be supplied to muscle cells either by utilizing stored muscle glycogen or supply from the liver via the bloodstream the energy value of one gram of carbohydrate is 4 calories.
In contrast to digestible carbohydrate, dietary fiber and other indigestible carbohydrates yield only minimal energy from intestinal microbial fermentation. Metabolism of fermentable fiber yields short chain fatty acids which are absorbed by the colon. Butyrate is utilized within the colonocyte while propionate and acetate are absorbed and transported to muscle and liver, respectively. Fermentable fiber provides approximately 2 cal/g of energy. Indigestible components of fiber benefit the intestinal tract by facilitating transport of nutrients and waste which lowers intramural pressure and promotes regularity.
Whole grains provide complex carbohydrate and tend to have more nutrients and fiber than refined grains. Eating plenty of whole grains may reduce your risk of heart disease.
The recommended amount of carbohydrate intake for a male and non-pregnant female recreational athlete it at least 60% of total energy intake, (assuming adequate intake is adequate). For endurance and strength-trained athletes 6-10g of carbohydrates per Kg of bodyweight.
If you want to lose fat, a useful guideline for lowering your calorie intake is to reduce your calories by at least 500, but not more than 1000 below your maintenance level. For people with only a small amount of weight to lose, 1000 calories will be too much of a deficit. As a guide to minimum calorie intake, the American College of Sports Medicine (ACSM) recommends that calorie levels never drop below 1200 calories per day for women or 1800 calories per day for men. Even these calorie levels are quite low.
The absolute minimum amount of carbs required per day for healthy brain function is 150g.
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