Although low-carbohydrate dieting is one of the most popular
approaches today, it’s nothing new to bodybuilders, who have used it
since the early ’60s. Vince Gironda, perhaps the premier trainer of that
era and owner of the fabled Vince’s Gym in Studio City, California, was
an advocate of low-carb dieting. He
used it himself when he competed in
bodybuilding contests in the early 1950s.
In fact, eating that way produced such prominent vascularity and
muscle striations on Vince that bodybuilding judges were confused as to
how to place him. There just wasn’t anyone around then who looked like
that. The bodybuilding world wasn’t ready for it.
The basis of the low-carb diet is simple: insulin control.
Although insulin has numerous functions, it is primarily a storage
hormone, and one of the things it helps to store is fat. The nutrient
that is most potent at eliciting an insulin release is carbohydrate,
particularly simple, or so-called high-glycemic-index, carb foods. They
are foods that lack fiber or contain large amounts of easily digested
starch that enter the blood rapidly, which triggers the release of
insulin. If you eat excess calories, the insulin helps convert them into
bodyfat.
Conversely, when insulin release is controlled, as occurs during a
low-carb diet, the metabolic door is opened to increased use of fat as
fuel—which leads to less bodyfat.
The idea of low-carb dieting dates back to the 1860s, when a
corpulent man named Banting, on the advice of his doctor, cut most of
the carbs from his diet and lost a lot of bodyfat. He wrote a small book
about his experiences, which became a best seller. Since then numerous
incarnations of the low-carb diet have appeared under various catchy
names; however, they all have one thing in common: They reduce carbs to
reduce insulin release.
A major controversy of low-carb dieting is the effect on physical
performance. Most people are surprised to learn that carbohydrates are
not essential in human nutrition. The body actually requires glucose or
alternative fuel sources, such as ketones from fat metabolism, lactate
and even glycerol, which makes up 10 percent of triglyceride structure.
All of those can either substitute for glucose or be converted into
glucose in the liver.
Among the possible substrates for the conversion to glucose are amino
acids derived from protein foods—or, in a worst-case scenario, from
muscle tissue. That’s one reason that higher protein is often suggested
for low-carb diets. Any excess protein that you take in can be converted
in the liver into glucose. In fact, about 57 percent of excess protein
eaten winds up being converted into glucose, most of which is oxidized,
or burned, in the liver.
Low-carb diets are well-known for producing ketosis, which involves
an increased production of ketone bodies. Ketones result from the
incomplete metabolism of fat. That can occur under pathological
conditions, as an effect of uncontrolled diabetes, but when it happens
during a low-carb diet, it is considered not only safe but also
desirable. The ketones supply an alternative energy source to glucose
that can be used readily by both the brain and the muscles.
In muscle, ketones exert an anticatabolic activity, helping to
prevent muscle loss. Certain parts of the central nervous system, as
well as red blood cells, still demand glucose, but that’s easily
supplied through the conversion of excess food amino acids into glucose.
Some amino acids, such a glutamine and alanine, are particularly
efficient at that. Leucine, a branched-chain amino acid noted for being
the primary stimulator of muscle protein synthesis, can also help to
maintain blood glucose levels during a diet.
Much of the confusion about the necessity of carbs for exercise comes from research done on endurance athletes.
Endurance events are far more apt to deplete muscle and liver glycogen,
which we know leads to a drop in performance. Athletes refer to it as
“hitting the wall,” since that’s the way it feels. Early studies that
compared carbohydrate-rich diets and low-carb diets usually found that
getting more carbs led to less fatigue and better performance. Indeed,
recognition of that eventually led to the concept of carb loading as a
way to improve performance through enhanced glycogen production in
muscles.
Carb loading involved dropping to a low-carb intake first, followed
by a high-carb intake, in the period leading up to an athletic event.
Later versions replaced the low-carb phase with moderate carbs combined
with increased activity to deplete muscle glycogen stores, which favors
supercompensation once you shift to the high-carb phase.
The truth, however, is that many endurance events take a lot of time
and so favor carb depletion. What about lifting weights? That involves
anaerobic metabolism, which does favor the use of glucose and glycogen
as energy.
Indeed, studies that have measured glycogen use during
weight training show muscle glycogen depletion of 24 to 40 percent,
depending on how long and how intense the workout is. One study
found that doing only three sets of biceps curls led to a 40 percent
depletion in glycogen in the biceps. It would appear that carbs are
required for optimal training intensity, since bodybuilding workouts are
fueled primarily by muscle glycogen and secondarily by circulating
glucose in the blood.
Even Dr. Robert Atkins, considered the guru of low-carb diets,
advised that those engaged in intense exercise require some carbs. The
problem is that nearly all studies that have found a drop in exercise
performance on low-carb diets were short term, lasting from three days
to two weeks. It takes some time for the body to make a metabolic switch
from using mainly carbs to other fuel sources, such as ketones. During
the initial few days on a severely restricted carb intake, most people
will experience premature fatigue during high-intensity training.
Typically, you feel fine during the first set but fade considerably
during the second and succeeding sets. That relates to a depletion in
muscle glycogen brought on by eliminating carbs.
After three to four weeks on even a ketogenic diet (30 grams or less a
day of carbs), the body adjusts to using alternative fuel sources,
mainly ketones. When that happens, training becomes significantly
easier, although never as efficient as when the muscles are fully loaded
with glycogen. An important point here is that if you eat carbs
intermittently during the initial changeover, the body doesn’t
efficiently adjust to the alternative fuels. A common practice among
bodybuilders is to have a carb day once or twice a week when they’re on a
low-carb or ketogenic diet, the rationale being to help replace
depleted glycogen and enable them to train harder. While that works, it
also prevents the full adjustment to using ketones and other alternative
energy sources. The net effect is that fat loss slows a bit—but not
enough to offset the benefits of the diet on body composition.
A lot of the stress of low-carb dieting could be relieved by taking
into account the fact that it takes about a month for the body to adjust
to using fuel sources other than carbs.
Much of the initial fatigue and weakness that occurs results from a diuretic effect induced by the diet.
Since each gram of glycogen is stored with 2.7 grams of water, when
glycogen begins to break down in response to the lack of carbs, the
water is excreted. Along with it go electrolytes, minerals that are
vital to muscle function, mainly sodium, potassium and magnesium. It’s
the loss of those minerals that produces the feelings of fatigue at the
start of low-carb diets. The easy remedy is to make sure you take in
three to four grams of sodium a day, along with at least 1,000
milligrams of potassium and 600 milligrams of magnesium, which is
required to retain the potassium in muscle.
Another way to avoid problems during low-carb diets is to make sure
you get enough protein. You need to increase protein intake during
low-calorie and low-carb diets to prevent losing muscle. Getting more
protein also provides a satiety effect, reducing appetite and making the
diet a bit easier. In practical terms, we’re talking about a gram of
protein per pound of bodyweight per day.
Getting too much protein, however, will prevent ketosis, since the
excess will be converted into glucose. The extra protein will not slow
the diet progress, however, since most of it will be oxidized in the
liver.
A recent study of elite artistic gymnasts compared the effects of
eating a diet containing less than 20 grams of carb a day with a typical
high-fat, high-carb Western diet for 30 days.
1 Of interest
to bodybuilders, it focused on any negative effects of the low-carb plan
on strength and power performance. The gymnasts underwent various tests
of strength and power both before and after the test period.
At the end of 30 days the results showed no performance
differences between the ketogenic diet and the high-carb, high-fat
Western diet. The gymnasts did, however, supplement both sodium and
potassium, as well as taking several other vitamin and mineral
supplements and herbs. They also ate a high-protein diet: 2.8 grams per
kilogram—2.2 pounds—of bodyweight.
Should you consider staying on low carbs year-round? While it’s
definitely the way to go in terms of losing excess bodyfat, the diet is
not ideal for building muscle. If you stay on it and avoid carb days,
you won’t get the benefits of insulin, which include an anticatabolic
action in muscle as well as an anabolic effect in the presence of high
blood amino acids. In addition, you need some carb for muscle glycogen
repletion. Without it, your muscles won’t fully recover between training
sessions. While ketones and other sources of energy, such as lactate
and glycerol, can help to replete depleted muscle glycogen stores, that
may not be enough for many people.
Carbs also promote the activity of intramuscular IGF-1, an anabolic
hormone required for complete muscle recovery and growth. Last, but not
least, for long-term high-intensity training, nothing beats carbs as an
energy source and for preventing premature muscle fatigue. The optimal
intake of carbs for nondieting bodybuilding purposes is four to seven
grams per kilogram of bodyweight daily, depending on body size and how
much training you do.
—Jerry Brainum
1 Paoli, A., et al. (2012). Ketogenic diet does not affect strength performance in elite artistic gymnasts.
J Int Soc Sports Nut. 9:34
©,2015 Jerry Brainum. Any reprinting in any type of media, including electronic and foreign is expressly prohibited
Have you been ripped off by supplement makers whose products don’t
work as advertised? Want to know the truth about them? Check out Jerry Brainum's book Natural Anabolics, available at JerryBrainum.com.
The Applied Ergogenics blog is a collection of articles written and
published by Jerry Brainum over the past 20 years. These articles have appeared
in Muscle and Fitness, Ironman, and other magazines. Many of the posts on the
blog are original articles, having appeared here for the first time. For Jerry’s
most recent articles, which are far more in depth than anything that appears on
this blog site, please subscribe to his Applied Metabolics Newsletter, at www.appliedmetabolics.com. This
newsletter, which is more correctly referred to as a monthly e-book, since its
average length is 35 to 40 pages, contains the latest findings about nutrition,
exercise science, fat-loss, anti-aging, ergogenic aids, food supplements, and
other topics. For 33 cents a day you get the benefit of Jerry’s 53 years of
writing and intense study of all matters pertaining to fitness,health,
bodybuilding, and disease prevention.
Want more evidence-based information on
exercise science, nutrition and food supplements, ergogenic aids, and
anti-aging research? Check out Applied Metabolics Newsletter at www.appliedmetabolics.com
Please share this blog on facebook
