The most frequent criticism of today’s popular low-carbohydrate diets is that they’re antithetical to optimum body chemistry. The idea is that since carbohydrates are undeniably the most readily available fuel source, not eating enough carbs leads to a host of physical and mental impairments, such as fatigue and a decrease in training intensity.Most nutrition authorities say that the ideal diet contains 55 to 60 percent carbohydrate. The preferred forms have the least effect on insulin secretion, usually because of their naturally higher fiber content. One way to figure out which carbs are best to eat is to consult a glycemic index, or GI, chart.
The glycemic index assigns numbers based on how rapidly a carb is absorbed into the blood compared with glucose, which is assigned the number 100. The primary problem with depending on GI numbers is that they apply only to carbs eaten alone, without any protein or fat. Protein and fat slow down carb absorption significantly, thus making GI numbers irrelevant. A more realistic way to view carbs is by consulting their glycemic load number, which shows the concentration of carbs contained in a specific food portion. For example, carrots have a high GI number, but they contain few carbs per typical portion. As such, they also have a low glycemic load number, suggesting that they exert little or no influence on blood glucose levels or insulin release.
With all the admonitions about the importance of carbohydrate intake, you would think that carbs are an essential nutrient. The truth is, though, that essential carb intake hasn’t been identified, as it has for fats and protein, simply because carbs can be synthesized in the liver from protein and, to a lesser degree, from fat in a process called gluconeogenesis. Some studies show that about 57 percent of excess dietary protein is converted to glucose, the carb that circulates in the blood(although this figure in now in doubt).Ten percent of glycerol, the triglyceride molecule, converts to glucose in the liver. Even by-products of exercise metabolism, such as lactate, readily convert into glucose in the liver.
What’s really important about carb foods is not the carbohydrate per se but the nutrients found in unprocessed carb foods, such as fruits, vegetables and whole grains. They contain fiber and myriad impressive health-preserving nutrients that fall under the umbrella term phytonutrients, such as flavonoids. Processed carbs, such as the abomination known as high-fructose corn syrup, have zero redeeming characteristics and are a primary factor in today’s obesity epidemic.
What would happen if you eliminated carbs from your diet? Surely that would induce metabolic derangement. Many studies examining the relationship between exercise and carbs have demonstrated that eliminating carbs does indeed lead to a significant drop in energy and training intensity. A lot of them are meaningless, however, because they were all short-term—often lasting no more than a week.
People who’ve eaten large amounts of carbs are sugar burners and may experience initial fatigue if their sugar or carb sources are abruptly removed. The body needs time to adjust to using another type of fuel—fat. The metabolic switchover takes about two to three weeks, during which most people feel some level of fatigue and lassitude. If you continue the diet and take certain precautions, however, the symptoms disappear.
That the human body is capable of adapting to a depletion of carbs is evident from the Inuit, or Eskimo, people, whose traditional diet contained about 85 percent fat and 15 percent protein. Despite the lack of carbs—fruits and veggies aren’t readily available in the Arctic—they thrived. Their high intake of fatty fish was the first found evidence of the benefits of omega-3 fatty acids, since the Inuit showed far lower rates of cardiovascular mortality than people living in Denmark, where the diet was more typically Western.
In 1929 an anthropologist named Vilhjalmur Stefansson returned from living with the Inuit for more than five years. During that time, he and an associate lived entirely on the native diet, with no side effects, with the exception of the first two weeks on the diet, when he began to feel ill. It turned out that the sick feeling came from a complete lack of fat intake, and when they replaced the fat, the symptoms dissipated. When he returned, he wrote about the Intuit diet extensively. To silence scientific skepticism at the time, Stefansson and an associate, Karsen Anderson, voluntarily committed themselves to a metabolic ward at Bellevue hospital in New York, where they ate the carb-free Inuit diet for a year under medical scrutiny. The diet they consumed contained 100-140 grams of protein; 200-300 grams of fat; and only 7-12 grams of carbs each day. Total calories they consumed each day was 2,000 to 3,100. This averages 15 to 25% protein; 75-85% fat; and 1-2% carbs.They showed no adverse effects on the diet, not even a vitamin C deficiency, which was predicted to occur after three months. In an article about the effects of the diet reported in the Journal of Biological Chemistry, Stefannsson was described as having "soft and flabby muscles."
But what of exercise? It’s one thing to sit around in a hospital ward, but what happens if you cut out carbs and try to train at the gym? Studies have examined that aspect of low-carb diets and found surprisingly few adverse effects, as long as a few other factors are accounted for.
The first is time for adaptation, starting with the two to three weeks the body needs to switch over to using fat instead of carbs as an energy source. Indeed, including carbs every few days prevents full metabolic adaptation to fat as a primary fuel source.
It’s also important to ensure adequate mineral, or electrolyte, intake. Low-carb diets are famous for their diuretic effect. That loss of water is often attributed to a breakdown of stored glycogen, which is stored with 2.7 grams of water for every gram of glycogen. But along with the water go electrolytes, such as sodium, magnesium and potassium, which play vital roles in nerve transmission. When they’re lacking, weakness and lassitude soon follow—along with more severe and even life-threatening effects.
Maintaining a high level of electrolytes also helps preserve lean mass, or muscle. Potassium is particularly important, but without magnesium you can’t retain potassium; you need them both. Adding calcium may also help because the lack of dairy foods limits calcium intake. Among other functions, calcium is required for muscle contraction and to help ward off muscle cramps.
The other key to an optimal low-carb diet for training is a higher protein intake. As you reduce calories or carbs, you must increase protein. That buffers you against nitrogen loss, which would lead to muscle breakdown, or catabolism. The body needs the excess protein converted in the liver to glucose for brain and central-nervous-system operation. Frequent protein meals also suppress appetite, which makes dieting easier.
One aspect that must be considered is the relationship between carb intake and glycogen synthesis. Without carbs, glycogen synthesis is stymied. Insufficient glycogen means lack of muscle pump, decreased recovery and lack of training intensity, since anaerobic exercise—such as bodybuilding workouts—relies on muscle glycogen stores. More recent studies also show that you need to ingest post-workout carbs to promote the intramuscular release of insulinlike growth factor-1 (IGF-1), which is required for complete muscle recovery and repair following training.
The solution is simple. Eat the majority of your carbohydrate foods before and after activity and concentrate on protein when you’re not active. That way you burn bodyfat at a maximum rate while getting the carbs you need to train hard. Also be aware that any carbs you get within the initial two hours after a workout go straight into glycogen replenishment. Carbs taken in at that time do not hinder fat metabolism, contrary to what some have stated.
©,2013 Jerry Brainum.Any reprinting in any type of media, including electronic and foreign is expressly prohibited.
Vilhjalmur Stefansson
