Note: This article is being re-written as some items are out of date. Please check back later for the revised article.
Carbohydrates - do we really need them?
We need protein, fats, minerals, enzymes, vitamins, but we do NOT need carbohydrates!
There is no medical condition such as "Carbohydrate Deficiency".
The body can manufacture any carbohydrates it may need from proteins, and a low-carbohydrate diet will result in fat loss, reduced risk of diabetes, and many other health benefits.
How carbohydrates are used
When we exercise, the body uses carbohydrate, fat and protein to make ATP (adenosine triphosphate).
It is from the energy released by the breakdown of ATP that allows muscle cells to contract. However, each nutrient has unique properties that determine how it gets converted to ATP.
Carbohydrate is the main nutrient that fuels exercise of a moderate to high intensity, while fat can fuel low intensity exercise for long periods of time.
Proteins are generally used to maintain and repair body tissues, and are not normally used to power muscle activity.
Because the body can not easily store ATP (and what is stored gets used up within a few seconds), it is necessary to continually create ATP during exercise.
In general, the two major ways the body converts nutrients to energy are:
- Aerobic metabolism (with oxygen)
- Anaerobic metabolism (without oxygen)
These two pathways can be further divided. Usually it is a combination of energy systems that supply the fuel needed for exercise, with the intensity and duration of the exercise determining which method gets used at the time.
ATP-CP Anaerobic Energy Pathway
The ATP-CP energy pathway (sometimes called the phosphate system) supplies about 10 seconds worth of energy and is used for short bursts of exercise such as a 100 meter sprint.
This pathway does not need oxygen to create ATP. For the first 2 or 3 seconds, any ATP stored in the muscle is used, then it uses CP (Creatine Phosphate) to resynthesize ATP for another 6 to 8 seconds when the CP runs out.
After the ATP and CP are used the body will switch to either aerobic or anaerobic metabolism (glycolysis) to continue to create ATP to fuel exercise.
Anaerobic Metabolism - Glycolysis
The anaerobic energy pathway, or glycolysis, creates ATP exclusively from carbohydrates, with lactic acid being a by-product.
Anaerobic glycolysis provides energy by the (partial) breakdown of glucose without needing any oxygen.
Anaerobic metabolism produces energy for short, high-intensity bursts of activity lasting no more than several minutes before the lactic acid build-up reaches the "lactate threshold" and muscle pain, burning and fatigue make it difficult to maintain such intensity.
Aerobic metabolism fuels most of the energy needed for long duration exercise, using oxygen to convert carbohydrates, fats and protein to ATP.
This takes longer than the anaerobic systems, because of reliance on the blood to deliver oxygen to the working muscles before ATP can be created.
Aerobic metabolism is used primarily during endurance exercise, which is generally less intense and can continue for long periods of time.
Athletes move through these metabolic pathways, starting with anaerobic metabolism, then as breathing and heart rate increase, more oxygen becomes available and aerobic metabolism kicks in, continuing until the lactate threshold is reached.
After the lactate threshold is surpassed, where ATP is used faster than the blood can deliver oxygen, then anaerobic metabolism begins again until lactic acid levels rise, forcing the athlete to reduce intensity to remove lactic acid build-up.
Fueling the Energy Systems
Nutrients get converted to ATP based upon the intensity and duration of activity, with carbohydrate as the main nutrient fueling exercise of a moderate to high intensity, and fat providing energy during exercise that occurs at a lower intensity.
Fat is a great fuel for endurance events, but not for high intensity exercise. At low intensity, e.g. below 50% of maximum heart rate, there is usually enough stored fat to fuel this exercise for many hours, as long as sufficient oxygen is delivered for fat metabolism.
As intensity is increased, carbohydrate metabolism takes over, and although more efficient than fat metabolism, has more limited energy stores.
Glycogen (stored carbohydrate) can fuel up to two hours of moderate to moderate-high exercise, then stored carbohydrates are gone and glycogen depletion occurs.
If those carbohydrates are not replaced, we may "hit the wall," but if we can replenish carbohydrates as we go, we can moderate to high intensity exercise for a longer time.
Eating easily digestible carbohydrates during moderate endurance exercise is important if the activity lasts more than a few hours, otherwise we must reduce intensity to switch back to fat metabolism if we want to keep going.
As exercise intensity increases, carbohydrate metabolism efficiency drops off and anaerobic metabolism increases, as the body can not provide oxygen fast enough to use either fat or carbohydrate metabolism easily.
Carbohydrates can produce almost 20 times more ATP per gram if metabolized in the presence of high oxygen than when produced in the anaerobic environment that occurs during intense efforts (sprinting).
Training allows energy systems to adapt, becoming more efficient and allowing increased exercise duration at increased intensity.
Unused Carbohydrates Stored as Fat
So carbohydrates are a great fuel, but if we consume too many carbs without the appropriate exercise, what happens to the carbs?
Excess carbohydrates are stored by the liver as fat!
The food list following will give some idea of carbs and fibre.
Amounts are approximate because content varies.
One slice of bread - 12.5 grams total, of which 10 grams are starch and less than one gram is fibre
One cup of pasta - 43 grams total, of which 36 grams are starch and 2.5 grams are fibre
One medium apple - 19 grams total, of which eight grams are starch and three grams are fibre
One Snickers candy bar - 63.5 total grams, of which 53 grams are sugar, two grams are fibre
One cup of raisin bran cereal - 43 grams total, of which seven grams are fibre, 17 grams are starch and 16 grams are sugar
One cup of sugar frosted corn flake cereal - 28 grams total, of which 15 grams are starch, one gram is fibre, 12 grams are sugar
One four ounce glass of red wine - three grams total, of which, less than one gram is sugar
One eight ounce serving of low fat milk - 12 grams total, of which 12 grams are lactose
One cup broccoli - six grams total, of which 2.5 grams are fibre and 1.5 grams are sugar
One cup green beans - eight grams total, of which four grams are fibre
One cup sweet corn - 31 grams total, of which 21 grams are starch, three grams are fibre
Two cups lettuce - two grams total, of which one gram is fibre
One cup asparagus - four grams total, of which two grams are fibre
One medium orange - 15 grams total, of which three grams are fibre
One half medium grapefruit - nine grams total, of which 1.5 grams are fibre
One medium chocolate chip cookie - 16 grams total, of which seven grams are sugar
One cup strawberries - 12 grams total, of which three grams are fibre
One cup blueberries - 21 grams total, of which four grams are fibre and 15 grams are sugar
One half cup marinara sauce - 14 grams total, of which less than one gram is fibre
One medium tomato - five grams total, of which 1.5 grams are fibre
One medium potato with skin - 29 grams total, of which three grams are fibre, 25 grams are starch
One cup carrots - 12 grams total, of which 3.5 grams are fibre and two grams are starch
One slice of an apple pie - 40 grams total, of which 18 grams are sugar
One eight ounce cup of orange juice - 26 grams total, of which 21 grams are from fruit sugars
One cup of dry beans like pinto beans or navy beans - 47 grams total, of which 19 grams are fibre, 28 grams are starch
On a zero-carb diet, we force the body to burn fat.
Sounds great for a fast weight-loss diet, but there is a major proble: Muscle wastage.
When the body needs some fast energy, and there is not enough glucose in the blood, then the fastest way to get what the body needs is to break down muscle, which is the last thing we want.
Better to break down fat, but this is a slower process, so to prevent muscle wastage, we should keep some carbohydrates in the diet, but not too much.
We have discussed carbohydrates for athletes, but now we need to talk about everyday people who perform everyday activities.
Lean Machine's recommendation is 25 grams of carbohydrates daily to prevent muscle from being broken down and wasted.
One apple a day will give us about our daily dose of carbohydrates with the extra we get from vegetables, etc.
For body-builders, up to 50 grams daily.
For those wanting to lose weight, less than 25 grams daily.
For those with any type of cancer, zero sugar and zero carbohydrates. All sugar feeds cancers.
Foods to avoid:
Most fruit juices, which have high sugar and/or fructose, and often with added sugar. When juice is swallowed, it goes straight down to the stomach without being pre-digested by saliva.
Juice is also deficient in fibre, and we need fibre to slow down the uptake of carbohydrates.
Too many carbs too fast causes a sudden spike of insulin, which makes us fat.
Any foods containing high sugar, high fructose or high starches should be avoided.
Typically this includes all sugars, excess fruits, all grain products (anything made with flour), potatoes and pasta.
All foods containing MSG should be avoided, and this includes nearly all processed food and almost all fast food. MSG (monosodium glutamate) again spikes insulin and makes us fat.
There are many healthy alternatives, such as fresh vegetables, and one peice of fruit daily, more if we are going to the gym for a decent workout.
Last Updated: 9th December 2016. Copyright © 1999-2019 Brenton Wight - Lean Machine
LeanMachine is not a doctor, and everyone should consult with their own health professional before taking any product to ensure there is no conflict with existing prescription medication.
LeanMachine has been studying nutrition and health since 2011 and has completed many relevant studies including:
Open2Study, Australia - Food, Nutrition and Your Health
RMIT University, Australia - Foundations of Psychology
Swinburne University of Technology, Australia - Chemistry - Building Blocks of the World
University of Washington, USA - Energy, Diet and Weight
Johns Hopkins Bloomberg School of Public Health, USA - Health Issues for Aging Populations
Johns Hopkins Bloomberg School of Public Health, USA - International Nutrition
Johns Hopkins Bloomberg School of Public Health, USA - Methods in Biostatistics I
Johns Hopkins Bloomberg School of Public Health, USA - Methods in Biostatistics II
Johns Hopkins Bloomberg School of Public Health, USA - Principles of Human Nutrition
TUFTS University, USA - Nutrition and Medicine
TUFTS University, USA - Lipids/Cardiovascular Disease I and Lipids/Cardiovascular Disease II
Technical Learning College, USA - Western Herbology, Identification, Formulas
Bath University, England - Inside Cancer
WebMD Education - The Link Between Stroke and Atrial Fibrillation
Leiden University Medical Center, Netherlands - Anatomy of the Abdomen and Pelvis
LeanMachine has now read thousands of studies, journals and reports related to health and nutrition and this research is ongoing.